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1.
Int J Behav Nutr Phys Act ; 19(1): 128, 2022 09 29.
Artículo en Inglés | MEDLINE | ID: mdl-36175996

RESUMEN

BACKGROUND: The e-coachER trial aimed to determine whether adding web-based behavioural support to exercise referral schemes (ERS) increased long-term device-measured physical activity (PA) for patients with chronic conditions, compared to ERS alone, within a randomised controlled trial. This study explores the mechanisms of action of the e-coachER intervention using measures of the behaviour change processes integral to the intervention's logic model. METHODS: Four hundred fifty adults with obesity, diabetes, hypertension, osteoarthritis or history of depression referred to an ERS were recruited in Plymouth, Birmingham and Glasgow. The e-coachER intervention comprising 7-Steps to Health was aligned with Self-Determination Theory and mapped against evidence-based behaviour change techniques (BCTs). Participants completed questionnaires at 0, 4, and 12 months to assess PA and self-reported offline engagement with core BCTs in day-to-day life (including action planning and self-monitoring) and beliefs relating to PA (including perceived importance, confidence, competence, autonomy and support). We compared groups at 4 and 12 months, controlling for baseline measures and other covariates. Mediation analysis using the product of coefficients method was used to determine if changes in process variables mediated intervention effects on moderate to vigorous physical activity (MVPA) recorded by accelerometer and self-report at 4- and 12-months. RESULTS: The internal reliability (Cronbach's alpha) for all multi-item scales was > 0.77. At 4-months, those randomised to e-coachER reported higher levels of PA beliefs relating to importance (1.01, 95% confidence interval (CI): 0.42 to 1.61, p = 0.001), confidence (1.28, 95% CI: 0.57 to 1.98, p < 0.001), competence (1.61, 95% CI: .68 to 2.54, p = 0.001), availability of support (0.77, 95% CI: 0.07 to 1.48, p = 0.031), use of action planning (1.54, 95% CI: 0.23 to 2.85, p = 0.021) and use of self-monitoring (0.76, 95% CI: 0.19 to 1.32, p = 0.009) compared to ERS alone. There were no intervention effects on autonomous beliefs or perceived frequency of support, compared to ERS alone. At the 12-month follow-up, participants belief in the importance of PA was the only process measure to remain significantly higher in the e-coachER group when compared to ERS alone (0.75, 95% CI: 0.05 to 1.45). Intervention effects on perceived importance (2.52, 95% CI: 0.45 to 5.39), action planning (1.56, 95% CI: 0.10 to 3.54) and self-monitoring (1.92, 95% CI: 0.21 to 4.33) at 4-months significantly mediated change in accelerometer measured MVPA at 12-months (recorded in ≥ 10-min bouts). CONCLUSIONS: e-coachER led to some short-term changes in most process outcomes. Some of these processes also appeared to mediate e-coachER effects on changes in accelerometer measured MVPA. Further work should be carried out to understand how best to design and implement theoretically underpinned web-based physical activity promotion interventions within ERS. TRIAL REGISTRATION: ISRCTN, ISRCTN15644451 . Registered 12 February 2015.


Asunto(s)
Intervención basada en la Internet , Adulto , Ejercicio Físico , Humanos , Análisis de Mediación , Atención Primaria de Salud/métodos , Derivación y Consulta , Reproducibilidad de los Resultados
2.
Eur Arch Psychiatry Clin Neurosci ; 270(7): 921-932, 2020 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-31802253

RESUMEN

Recent genome-wide association studies have demonstrated that the genetic burden associated with depression correlates with depression severity. Therefore, conducting genetic studies of patients at the most severe end of the depressive disorder spectrum, those with treatment-resistant depression and who are prescribed electroconvulsive therapy (ECT), could lead to a better understanding of the genetic underpinnings of depression. Despite ECT being one of the most effective forms of treatment for severe depressive disorders, it is usually placed at the end of treatment algorithms of current guidelines. This is perhaps because ECT has controlled risk and logistical demands including use of general anaesthesia and muscle relaxants and side-effects such as short-term memory impairment. Better understanding of the genetics and biology of ECT response and of cognitive side-effects could lead to more personalized treatment decisions. To enhance the understanding of the genomics of severe depression and ECT response, researchers and ECT providers from around the world and from various depression or ECT networks, but not limited to, such as the Psychiatric Genomics Consortium, the Clinical Alliance and Research in ECT, and the National Network of Depression Centers have formed the Genetics of ECT International Consortium (Gen-ECT-ic). Gen-ECT-ic will organize the largest clinical and genetic collection to date to study the genomics of severe depressive disorders and response to ECT, aiming for 30,000 patients worldwide using a GWAS approach. At this stage it will be the largest genomic study on treatment response in depression. Retrospective data abstraction and prospective data collection will be facilitated by a uniform data collection approach that is flexible and will incorporate data from many clinical practices. Gen-ECT-ic invites all ECT providers and researchers to join its efforts.


Asunto(s)
Conjuntos de Datos como Asunto , Trastorno Depresivo/genética , Trastorno Depresivo/terapia , Terapia Electroconvulsiva , Estudio de Asociación del Genoma Completo , Estudios Multicéntricos como Asunto , Recolección de Datos , Humanos
3.
Proc Natl Acad Sci U S A ; 105(7): 2343-8, 2008 Feb 19.
Artículo en Inglés | MEDLINE | ID: mdl-18227506

RESUMEN

Proteins that share common ancestry may differ in structure and function because of divergent evolution of their amino acid sequences. For a typical diverse protein superfamily, the properties of a few scattered members are known from experiment. A satisfying picture of functional and structural evolution in relation to sequence changes, however, may require characterization of a larger, well chosen subset. Here, we employ a "stepping-stone" method, based on transitive homology, to target sequences intermediate between two related proteins with known divergent properties. We apply the approach to the question of how new protein folds can evolve from preexisting folds and, in particular, to an evolutionary change in secondary structure and oligomeric state in the Cro family of bacteriophage transcription factors, initially identified by sequence-structure comparison of distant homologs from phages P22 and lambda. We report crystal structures of two Cro proteins, Xfaso 1 and Pfl 6, with sequences intermediate between those of P22 and lambda. The domains show 40% sequence identity but differ by switching of alpha-helix to beta-sheet in a C-terminal region spanning approximately 25 residues. Sedimentation analysis also suggests a correlation between helix-to-sheet conversion and strengthened dimerization.


Asunto(s)
Proteínas de Unión al ADN/química , Proteínas Represoras/química , Proteínas Reguladoras y Accesorias Virales/química , Secuencia de Aminoácidos , Dicroismo Circular , Cristalografía por Rayos X , Modelos Moleculares , Datos de Secuencia Molecular , Estructura Terciaria de Proteína
4.
BMC Neurol ; 10: 88, 2010 Oct 07.
Artículo en Inglés | MEDLINE | ID: mdl-20929556

RESUMEN

BACKGROUND: There is a need for greater understanding of the impact of multiple sclerosis (MS) from the perspective of individuals with the condition. The South West Impact of MS Project (SWIMS) has been designed to improve understanding of disease impact using a patient-centred approach. The purpose is to (1) develop improved measurement instruments for clinical trials, (2) evaluate longitudinal performance of a variety of patient-reported outcome measures, (3) develop prognostic predictors for use in individualising drug treatment for patients, particularly early on in the disease course. METHODS: This is a patient-centred, prospective, longitudinal study of multiple sclerosis and clinically isolated syndrome (CIS) in south west England. The study area comprises two counties with a population of approximately 1.7 million and an estimated 1,800 cases of MS. Self-completion questionnaires are administered to participants every six months (for people with MS) or 12 months (CIS). Here we present descriptive statistics of the baseline data provided by 967 participants with MS. RESULTS: Seventy-five percent of those approached consented to participate. The male:female ratio was 1.00:3.01 (n = 967). Average (standard deviation) age at time of entry to SWIMS was 51.6 (11.5) years (n = 961) and median (interquartile range) time since first symptom was 13.3 (6.8 to 24.5) years (n = 934). Fatigue was the most commonly reported symptom, with 80% of participants experiencing fatigue at baseline. Although medication use for symptom control was common, there was little evidence of effectiveness, particularly for fatigue. Nineteen percent of participants were unable to classify their subtype of MS. When patient-reported subtype was compared to neurologist assessment for a sample of participants (n = 396), agreement in disease sub-type was achieved in 63% of cases. There were 836 relapses, reported by 931 participants, in the twelve months prior to baseline. Twenty-three percent of the relapsing-remitting group and 12% of the total sample were receiving disease-modifying therapy at baseline. CONCLUSIONS: Demographics of this sample were similar to published data for the UK. Overall, the results broadly reflect clinical experience in confirming high symptom prevalence, with relatively little complete symptom relief. Participants often had difficulty in defining MS relapses and their own MS type.


Asunto(s)
Esclerosis Múltiple , Evaluación de Resultado en la Atención de Salud/métodos , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Inglaterra , Femenino , Humanos , Estudios Longitudinales , Masculino , Persona de Mediana Edad , Esclerosis Múltiple/tratamiento farmacológico , Esclerosis Múltiple/fisiopatología , Adulto Joven
5.
Health Technol Assess ; 24(63): 1-106, 2020 11.
Artículo en Inglés | MEDLINE | ID: mdl-33243368

RESUMEN

BACKGROUND: There is modest evidence that exercise referral schemes increase physical activity in inactive individuals with chronic health conditions. There is a need to identify additional ways to improve the effects of exercise referral schemes on long-term physical activity. OBJECTIVES: To determine if adding the e-coachER intervention to exercise referral schemes is more clinically effective and cost-effective in increasing physical activity after 1 year than usual exercise referral schemes. DESIGN: A pragmatic, multicentre, two-arm randomised controlled trial, with a mixed-methods process evaluation and health economic analysis. Participants were allocated in a 1 : 1 ratio to either exercise referral schemes plus e-coachER (intervention) or exercise referral schemes alone (control). SETTING: Patients were referred to exercise referral schemes in Plymouth, Birmingham and Glasgow. PARTICIPANTS: There were 450 participants aged 16-74 years, with a body mass index of 30-40 kg/m2, with hypertension, prediabetes, type 2 diabetes, lower limb osteoarthritis or a current/recent history of treatment for depression, who were also inactive, contactable via e-mail and internet users. INTERVENTION: e-coachER was designed to augment exercise referral schemes. Participants received a pedometer and fridge magnet with physical activity recording sheets, and a user guide to access the web-based support in the form of seven 'steps to health'. e-coachER aimed to build the use of behavioural skills (e.g. self-monitoring) while strengthening favourable beliefs in the importance of physical activity, competence, autonomy in physical activity choices and relatedness. All participants were referred to a standard exercise referral scheme. PRIMARY OUTCOME MEASURE: Minutes of moderate and vigorous physical activity in ≥ 10-minute bouts measured by an accelerometer over 1 week at 12 months, worn ≥ 16 hours per day for ≥ 4 days including ≥ 1 weekend day. SECONDARY OUTCOMES: Other accelerometer-derived physical activity measures, self-reported physical activity, exercise referral scheme attendance and EuroQol-5 Dimensions, five-level version, and Hospital Anxiety and Depression Scale scores were collected at 4 and 12 months post randomisation. RESULTS: Participants had a mean body mass index of 32.6 (standard deviation) 4.4 kg/m2, were referred primarily for weight loss and were mostly confident self-rated information technology users. Primary outcome analysis involving those with usable data showed a weak indicative effect in favour of the intervention group (n = 108) compared with the control group (n = 124); 11.8 weekly minutes of moderate and vigorous physical activity (95% confidence interval -2.1 to 26.0 minutes; p = 0.10). Sixty-four per cent of intervention participants logged on at least once; they gave generally positive feedback on the web-based support. The intervention had no effect on other physical activity outcomes, exercise referral scheme attendance (78% in the control group vs. 75% in the intervention group) or EuroQol-5 Dimensions, five-level version, or Hospital Anxiety and Depression Scale scores, but did enhance a number of process outcomes (i.e. confidence, importance and competence) compared with the control group at 4 months, but not at 12 months. At 12 months, the intervention group incurred an additional mean cost of £439 (95% confidence interval -£182 to £1060) compared with the control group, but generated more quality-adjusted life-years (mean 0.026, 95% confidence interval 0.013 to 0.040), with an incremental cost-effectiveness ratio of an additional £16,885 per quality-adjusted life-year. LIMITATIONS: A significant proportion (46%) of participants were not included in the primary analysis because of study withdrawal and insufficient device wear-time, so the results must be interpreted with caution. The regression model fit for the primary outcome was poor because of the considerable proportion of participants [142/243 (58%)] who recorded no instances of ≥ 10-minute bouts of moderate and vigorous physical activity at 12 months post randomisation. FUTURE WORK: The design and rigorous evaluation of cost-effective and scalable ways to increase exercise referral scheme uptake and maintenance of moderate and vigorous physical activity are needed among patients with chronic conditions. CONCLUSIONS: Adding e-coachER to usual exercise referral schemes had only a weak indicative effect on long-term rigorously defined, objectively assessed moderate and vigorous physical activity. The provision of the e-coachER support package led to an additional cost and has a 63% probability of being cost-effective based on the UK threshold of £30,000 per quality-adjusted life-year. The intervention did improve some process outcomes as specified in our logic model. TRIAL REGISTRATION: Current Controlled Trials ISRCTN15644451. FUNDING: This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 24, No. 63. See the NIHR Journals Library website for further project information.


When health-care professionals refer patients with chronic conditions to an exercise referral scheme, the effects on long-term increases in physical activity are limited. We therefore developed the e-coachER support package to add to usual exercise referral schemes and to prompt the use of skills such as self-monitoring and goal-setting. This package was also intended to empower patients to increase their levels of physical activity long term. The seven-step programme was delivered online (via an interactive website). As part of the package, we mailed participants a guide for accessing the online programme, a pedometer and a fridge magnet with a notepad to record physical activity. We aimed to determine whether or not adding the e-coachER support to usual exercise referral schemes resulted in lasting changes in moderate and vigorous physical activity and whether or not it offers good value for money compared with exercise referral schemes alone. A total of 450 inactive individuals were recruited across Plymouth, Birmingham and Glasgow and were referred to an exercise referral scheme for the following participant-reported main reasons: weight loss (50%), low mood (19%), osteoarthritis (12%), type 2 diabetes (10%) and high blood pressure (8%). Half of the individuals were given access to the e-coachER support and the other half were not. All individuals were mailed a wrist-worn movement sensor (accelerometer) to wear for 1 week and a survey to assess other outcomes at the start of the study as well as at 4 and 12 months post randomisation. At the start of the study, the participants were inactive and most had multiple health conditions. The participants had an average body mass index of 33 kg/m2 and an average age of 50 years. Most (83%) were white. Participants with access to e-coachER support were only slightly more active at 12 months than those who did not have access, but we cannot be confident in the findings because we had data from fewer participants than planned. The lack of a clear effect may have been as a result of around one-third of participants not accessing the website, but otherwise there was reasonable engagement. The provision of the e-coachER support package led to an additional cost of £439 per participant over a 12-month period.


Asunto(s)
Enfermedad Crónica/terapia , Ejercicio Físico , Tutoría/métodos , Telemedicina/métodos , Acelerometría , Adolescente , Adulto , Anciano , Análisis Costo-Beneficio , Femenino , Humanos , Masculino , Salud Mental , Persona de Mediana Edad , Calidad de Vida , Derivación y Consulta , Conducta Sedentaria , Autoinforme , Factores de Tiempo , Programas de Reducción de Peso , Adulto Joven
6.
Mol Immunol ; 85: 185-195, 2017 05.
Artículo en Inglés | MEDLINE | ID: mdl-28282643

RESUMEN

Thymic cellularity is influenced by a variety of biological and environmental factors, such as age and stress; however, little is known about the molecular genetic mechanisms that regulate this process. Immediate early genes of the Early growth response (Egr) family have critical roles in immune function and response to environmental stress. The transcription factors, Egr1, Egr2 and Egr3, play roles in the thymus and in peripheral T-cell activation. Nab2, which binds Egrs 1, 2, and 3 as a co-regulator of transcription, also regulates peripheral T-cell activation. However, a role for Nab2 in the thymus has not been reported. Using Nab2-deficient (KO) mice we found that male Nab2KO mice have reduced thymus size and decreased numbers of thymocytes, compared with age-matched wildtype (WT) mice. Furthermore, the number of thymocytes in Nab2KO males decreases more rapidly with age. This effect is sex-dependent as female Nab2KO mice show neither reduced thymocyte numbers nor accelerated thymocyte loss with age, compared to female WT littermates. Since stress induces expression of Nab2 and the Egrs, we examined whether loss of Nab2 alters stress-induced decrease in thymic cellularity. Restraint stress induced a significant decrease in thymic cellularity in Nab2KO and WT mice, with significant changes in the thymocyte subset populations only in the Nab2KO mice. Stress reduced the percentage of DP cells by half and increased the percentage of CD4SP and CD8SP cells by roughly three-fold in Nab2KO mice. These findings indicate a requirement for Nab2 in maintaining thymocyte number in male mice with age and in response to stress.


Asunto(s)
Envejecimiento/metabolismo , Proteínas de Neoplasias/metabolismo , Proteínas Represoras/metabolismo , Estrés Psicológico/metabolismo , Timo/patología , Envejecimiento/inmunología , Envejecimiento/patología , Animales , Femenino , Citometría de Flujo , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Proteínas de Neoplasias/inmunología , Proteínas Represoras/inmunología , Restricción Física , Caracteres Sexuales , Estrés Psicológico/inmunología , Estrés Psicológico/patología , Timo/inmunología , Timo/metabolismo
7.
Artículo en Inglés | MEDLINE | ID: mdl-16364696

RESUMEN

A high performance liquid chromatographic assay for the quantitative determination of apomorphine in human plasma is described. Sample clean-up and concentration was optimised using solid-phase extraction on C18 cartridges, enabling rapid and sensitive determination of apomorphine and potential metabolites. The limit of apomorphine quantification, using fluorescence detection, was 0.5 ng/mL. The assay was stability-indicating, and allowed the detection of analytes in the presence of commonly co-administered anti-Parkinsonian drugs. Apomorphine was stable in frozen plasma containing 0.14% (w/v) ascorbic acid for 98 days, and through four freeze-thaw cycles. The assay has been used in clinical pharmacokinetic studies of apomorphine in patients with Parkinson's disease, and in preliminary studies of novel apomorphine delivery devices in volunteers.


Asunto(s)
Apomorfina/sangre , Apomorfina/farmacocinética , Cromatografía Líquida de Alta Presión/métodos , Enfermedad de Parkinson/tratamiento farmacológico , Apomorfina/uso terapéutico , Ácido Ascórbico , Estabilidad de Medicamentos , Congelación , Humanos , Enfermedad de Parkinson/sangre , Reproducibilidad de los Resultados , Sensibilidad y Especificidad
8.
Neuropsychopharmacology ; 37(10): 2285-98, 2012 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-22692564

RESUMEN

The immediate-early gene early growth response 3 (Egr3) is associated with schizophrenia and expressed at reduced levels in postmortem patients' brains. We have previously reported that Egr3-deficient (Egr3(-/-)) mice display reduced sensitivity to the sedating effects of clozapine compared with wild-type (WT) littermates, paralleling the heightened tolerance of schizophrenia patients to antipsychotic side effects. In this study, we have used a pharmacological dissection approach to identify a neurotransmitter receptor defect in Egr3(-/-) mice that may mediate their resistance to the locomotor suppressive effects of clozapine. We report that this response is specific to second-generation antipsychotic agents (SGAs), as first-generation medications suppress the locomotor activity of Egr3(-/-) and WT mice to a similar degree. Further, in contrast to the leading theory that sedation by clozapine results from anti-histaminergic effects, we show that H1 histamine receptors are not responsible for this effect in C57BL/6 mice. Instead, selective serotonin 2A receptor (5HT(2A)R) antagonists ketanserin and MDL-11939 replicate the effect of SGAs, repressing the activity in WT mice at a dosage that fails to suppress the activity of Egr3(-/-) mice. Radioligand binding revealed nearly 70% reduction in 5HT(2A)R expression in the prefrontal cortex of Egr3(-/-) mice compared with controls. Egr3(-/-) mice also exhibit a decreased head-twitch response to 5HT(2A)R agonist 1-(2,5-dimethoxy 4-iodophenyl)-2-amino propane (DOI). These findings provide a mechanism to explain the reduced sensitivity of Egr3(-/-) mice to the locomotor suppressive effects of SGAs, and suggest that 5HT(2A)Rs may also contribute to the sedating properties of these medications in humans. Moreover, as the deficit in cortical 5HT(2A)R in Egr3(-/-) mice aligns with numerous studies reporting decreased 5HT(2A)R levels in the brains of schizophrenia patients, and the gene encoding the 5HT(2A)R is itself a leading schizophrenia candidate gene, these findings suggest a potential mechanism by which putative dysfunction in EGR3 in humans may influence risk for schizophrenia.


Asunto(s)
Proteína 3 de la Respuesta de Crecimiento Precoz/deficiencia , Proteína 3 de la Respuesta de Crecimiento Precoz/genética , Hipnóticos y Sedantes/metabolismo , Actividad Motora/efectos de los fármacos , Receptor de Serotonina 5-HT2A/metabolismo , Animales , Clozapina/farmacología , Modelos Animales de Enfermedad , Humanos , Ketanserina , Masculino , Ratones , Ratones Transgénicos , Piperidinas , Esquizofrenia/metabolismo , Agonistas del Receptor de Serotonina 5-HT2 , Antagonistas de la Serotonina/farmacología
9.
Protein Eng Des Sel ; 24(9): 765-71, 2011 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-21676898

RESUMEN

Regions of amino-acid sequence that are compatible with multiple folds may facilitate evolutionary transitions in protein structure. In a previous study, we described a heuristically designed chameleon sequence (SASF1, structurally ambivalent sequence fragment 1) that could adopt either of two naturally occurring conformations (α-helical or ß-sheet) when incorporated as part of the C-terminal dimerization subdomain of two structurally divergent transcription factors, P22 Cro and λ Cro. Here we describe longer chameleon designs (SASF2 and SASF3) that in the case of SASF3 correspond to the full C-terminal half of the ordered region of a P22 Cro/λ Cro sequence alignment (residues 34-57). P22-SASF2 and λ(WDD)-SASF2 show moderate thermal stability in denaturation curves monitored by circular dichroism (T(m) values of 46 and 55°C, respectively), while P22-SASF3 and λ(WDD)-SASF3 have somewhat reduced stability (T(m) values of 33 and 49°C, respectively). (13)C and (1)H NMR secondary chemical shift analysis confirms two C-terminal α-helices for P22-SASF2 (residues 36-45 and 54-57) and two C-terminal ß-strands for λ(WDD)-SASF2 (residues 40-45 and 50-52), corresponding to secondary structure locations in the two parent sequences. Backbone relaxation data show that both chameleon sequences have a relatively well-ordered structure. Comparisons of (15)N-(1)H correlation spectra for SASF2 and SASF3-containing proteins strongly suggest that SASF3 retains the chameleonism of SASF2. Both Cro C-terminal conformations can be encoded in a single sequence, showing the plausibility of linking different Cro folds by smooth evolutionary transitions. The N-terminal subdomain, though largely conserved in structure, also exerts an important contextual influence on the structure of the C-terminal region.


Asunto(s)
Ingeniería de Proteínas/métodos , Proteínas Represoras/química , Proteínas Reguladoras y Accesorias Virales/química , Secuencia de Aminoácidos , Evolución Molecular , Modelos Moleculares , Datos de Secuencia Molecular , Resonancia Magnética Nuclear Biomolecular , Conformación Proteica , Pliegue de Proteína , Proteínas Represoras/genética , Proteínas Represoras/metabolismo , Alineación de Secuencia , Proteínas Reguladoras y Accesorias Virales/genética , Proteínas Reguladoras y Accesorias Virales/metabolismo
10.
Protein Sci ; 17(5): 803-12, 2008 May.
Artículo en Inglés | MEDLINE | ID: mdl-18369196

RESUMEN

Bacteriophage Cro proteins bind to target DNA as dimers but do not all dimerize with equal strength, and differ in fold in the region of the dimer interface. We report the structure of the Cro protein from Enterobacteria phage N15 at 1.05 A resolution. The subunit fold contains five alpha-helices and is closely similar to the structure of P22 Cro (1.3 A backbone room mean square difference over 52 residues), but quite different from that of lambda Cro, a structurally diverged member of this family with a mixed alpha-helix/beta-sheet fold. N15 Cro crystallizes as a biological dimer with an extensive interface (1303 A(2) change in accessible surface area per dimer) and also dimerizes in solution with a K(d) of 5.1 +/- 1.5 microM. Its dimerization is much stronger than that of its structural homolog P22 Cro, which does not self-associate detectably in solution. Instead, the level of self-association and interfacial area for N15 Cro is similar to that of lambda Cro, even though these two orthologs do not share the same fold and have dimer interfaces that are qualitatively different in structure. The common Cro ancestor is thought to be an all-helical monomer similar to P22 Cro. We propose that two Cro descendants independently developed stronger dimerization by entirely different mechanisms.


Asunto(s)
Colifagos/metabolismo , Proteínas de Unión al ADN/química , ADN/química , Proteínas Represoras/química , Proteínas Reguladoras y Accesorias Virales/química , Bacteriófago P22/metabolismo , Cristalografía por Rayos X , ADN/metabolismo , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/metabolismo , Dimerización , Estructura Secundaria de Proteína , Estructura Terciaria de Proteína , Subunidades de Proteína/química , Subunidades de Proteína/metabolismo , Proteínas Represoras/genética , Proteínas Represoras/metabolismo , Proteínas Reguladoras y Accesorias Virales/genética , Proteínas Reguladoras y Accesorias Virales/metabolismo
11.
Biochemistry ; 45(35): 10542-53, 2006 Sep 05.
Artículo en Inglés | MEDLINE | ID: mdl-16939206

RESUMEN

In the Cro protein family, an evolutionary change in secondary structure has converted an alpha-helical fold to a mixture of alpha-helix and beta-sheet. P22 Cro and lambda Cro represent the ancestral all-alpha and descendant alpha+beta folds, respectively. The major structural differences between these proteins are at the C-terminal end of the domain (residues 34-56), where two alpha-helices in P22 Cro align with two beta-strands in lambda Cro. We sought to assess the possibility that smooth evolutionary transitions could have converted the all-alpha structure to the alpha+beta structure through sequences that could adopt both folds. First, we used scanning mutagenesis to identify and compare patterns of key stabilizing residues in the C-terminal regions of both P22 Cro and lambda Cro. These patterns exhibited little similarity to each other, with structurally important residues in the two proteins most often occurring at different sequence positions. Second, "hybrid scanning" studies, involving replacement of each wild-type residue in P22 Cro with the aligned wild-type residue in lambda Cro and vice versa, revealed five or six residues in each protein that strongly destabilized the other. These results suggest that key stability determinants for each Cro fold are quite different and that the P22 Cro sequence strongly favors the all-alpha structure while the lambda Cro sequence strongly favors the alpha+beta structure. Nonetheless, we were able to design a "structurally ambivalent" sequence fragment (SASF1), which corresponded to residues 39-56 and simultaneously incorporated most key stabilizing residues for both P22 Cro and lambda Cro. NMR experiments showed SASF1 to stably fold as a beta-hairpin when incorporated into the lambda Cro sequence but as a pair of alpha-helices when incorporated into P22 Cro.


Asunto(s)
Alanina/genética , Proteínas de Unión al ADN/genética , Pliegue de Proteína , Proteínas/química , Proteínas Represoras/genética , Proteínas Virales/genética , Secuencias de Aminoácidos , Secuencia de Aminoácidos , Modelos Moleculares , Datos de Secuencia Molecular , Mutagénesis , Estructura Terciaria de Proteína , Homología de Secuencia de Aminoácido , Homología Estructural de Proteína , Proteínas Reguladoras y Accesorias Virales
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