Agonists of prostaglandin E2 receptors as potential first in class treatment for nephronophthisis and related ciliopathies.

Nephronophthisis (NPH) is an autosomal recessive tubulointerstitial nephropathy belonging to the ciliopathy disorders and known as the most common cause of hereditary end-stage renal disease in children. Yet, no curative treatment is available. The major gene, NPHP1, encodes a protein playing key functions at the primary cilium and cellular junctions. Using a medium-throughput drug-screen in NPHP1 knockdown cells, we identified 51 Food and Drug Administration-approved compounds by their ability to alleviate the cellular phenotypes associated with the loss of NPHP1; 11 compounds were further selected for their physicochemical properties. Among those compounds, prostaglandin E1 (PGE1) rescued ciliogenesis defects in immortalized patient NPHP1 urine-derived renal tubular cells, and improved ciliary and kidney phenotypes in our NPH zebrafish and Nphp1 knockout mouse models. Furthermore, Taprenepag, a nonprostanoid prostaglandin E2 receptor agonist, alleviated the severe retinopathy observed in Nphp1−/− mice. Finally, comparative transcriptomics allowed identification of key signaling pathways downstream PGE1, including cell cycle progression, extracellular matrix, adhesion, or actin cytoskeleton organization. In conclusion, using in vitro and in vivo models, we showed that prostaglandin E2 receptor agonists can ameliorate several of the pleotropic phenotypes caused by the absence of NPHP1; this opens their potential as a first therapeutic option for juvenile NPH-associated ciliopathies.

Curcumin and omega-3 polyunsaturated fatty acids as bioactive food components with synergistic effects on Alzheimer's disease.

Curcumin and omega-3 polyunsaturated fatty acids (ω-3 PUFA) are multifunctional compounds which play an important role in Alzheimer's disease (AD) and little has been addressed about the role of these two compounds together in the progression of the disease. There is evidence of the beneficial effect of combined administration of ω-3 PUFA and other dietary supplements such as vitamins and polyphenols in the prevention of AD, although much remains to be understood about their possible complementary or synergistic activity. Therefore, the objective of this work is to review the research focused on studying the effect and mechanisms of action of curcumin, ω-3 PUFA, and the combination of these nutraceutical compounds, particularly on AD, and to integrate the possible ways in which these compounds can potentiate their effect. The most important pathophysiologies that manifest in AD will be addressed, in order to have a better understanding of the mechanisms of action through which these bioactive compounds exert a neuroprotective effect.

Disparities on prostate cancer survival in Mexico: a retrospective cohort study.

OBJECTIVE: To estimate prostate cancer (PC) survival in Mexico and explore survival disparities according to the marginalization level of residence place. MATERIALS AND METHODS: A nationwide administrative claims database (4 110 men) whose PC treatment was financed by Seguro Popular between 2012-2016, was cross-linked to the National Mortality Registry up to December 2019. Patients were classified according to their oncological risk at diagnosis and the marginalization level of the residence municipality. Cox proportional hazards regression was used to estimate multivariable survival functions. RESULTS: Five-years PC survival (69%; 95%CI: 68,71%) ranged from 72% to 54% at very low and very high marginalization, respectively (p for trend<0.001). The lowest PC survival was observed in men with high-risk PC (47%; 95%CI: 33,66%) residents in very high marginalization municipalities. CONCLUSIONS: Overall, PC survival was lower than that reported in other Latin American countries. The distribution of oncologic risk and survival differences across marginalization levels suggests limited early detection and cancer health disparities.

Antioxidant addition improves cholesterol and astaxanthin stability in dry salted shrimp.

BACKGROUND: Traditional production of dry salted shrimp enhances cholesterol oxidation and astaxanthin degradation in the product. The aim of this study was to evaluate the effect of addition of the antioxidants butylhydroxytoluene (BHT) and tert-butylhydroquinone (TBHQ) to cooked shrimp on the formation of cholesterol oxidation products (COPs) and astaxanthin degradation during solar drying of shrimp. RESULTS: The added antioxidants significantly inhibited COPs formation after the product was boiled in brine. Smaller amounts of COPs were formed in antioxidant-treated shrimps (~-23%) as compared to untreated samples. The antioxidants continued to significantly inhibit COPs formation (~-39%) during sun drying. Similarly, TBHQ and BHT reduced by 51.3% and 37.2%, respectively, the degradation rate of astaxanthin, favoring a higher retention of this carotenoid in the final product. CONCLUSION: The use of the antioxidants BHT and TBHQ in the preparation of dry salted shrimp significantly inhibited the formation of COPs after cooking raw shrimp and during direct solar drying. They also protected astaxanthin contained in the cooked shrimp from photodegradation. These results are technologically relevant because it is possible to prepare a product with a higher content of astaxanthin and lower the presence of hazardous COPs. © 2022 Society of Chemical Industry.

Brucella melitensis invA gene (BME_RS01060) transcription is promoted under acidic stress conditions.

The invA gene of Brucella melitensis codes for a NUDIX (nucleoside diphosphate linked to moiety X) hydrolase related to invasiveness. The objective of this work was to evaluate invA transcription under acidic conditions. The invA gene transcription was up regulated at pH 3 and pH 5 observed with semiquantitative real-time PCR in B. melitensis 133 strain. Results indicated that invA gene transcription at pH 3 showed a basal and decreased transcription compared to that of pH 5 incubation. Transcription levels of the dnaK gene were similar to those obtained with invA gene. The survival rates of wild type and invA mutant strains at pH 5 were above 90% in all post-incubation times. In contrast, at pH 3 there was a time-dependent reduction on both strains at 15 min (P < 0.05). These results suggest that invA gene transcription is promoted under acidic conditions in Brucella melitensis.

Effect of CLA supplementation on factors related to vascular dysfunction in arteries of orchidectomized rats.

The vascular endothelium is a monolayer of flat epithelial cells located between the circulating blood and the underlying connective tissue. It conveys key functions that when impaired, lead to endothelial dysfunction. This condition is responsible for the pathogenesis of vascular diseases. The cardioprotective effect of sex hormones is widely known; hence, a murine orchidectomized model has been employed to study the effects caused by their deficiency. In the search for approaches to maintain vascular health, the effect of dietary fatty acids as CLA on cardiovascular diseases has been studied. Some proven beneficial properties of CLA are antioxidant, antiatherogenic and anti-inflammatory. Our objective was to evaluate the effect of a diet supplemented with 1.8 % (w/w) of CLA, administered during eight weeks, on the amount of cholesterol oxidation products (COPs) produced by orchidectomy and on factors related to vascular dysfunction in the aorta and the mesenteric arteries. The diet with CLA prevented the increase in prostanoids formation and maintained the normal physiological conditions of NO and antioxidant activity. In addition, it prevented the increase in cholesterol and COPs at the vascular wall. CLA-supplemented diet prevented the orchidectomy-induced alterations on prostanoids, NO and COPs and also improved the antioxidant activity. These findings could contribute to understand the mechanisms of actions of CLA involved in the prevention of cardiovascular diseases.

Invited review: Effect of antihypertensive fermented milks on gut microbiota.

Hypertension is a risk factor for the development of other cardiovascular diseases and remains one of the leading causes of death worldwide. Although genetic and environmental factors are associated with the development of hypertension, it has been recently recognized that gut microbiota (GM) may also have an effect on human health. In this sense, gut dysbiosis (a marked decrease in richness and diversity of GM) has been linked to different metabolic diseases, such as hypertension. Therefore, different studies have been pursued to reduce gut dysbiosis and diminish hypertension. Different strategies to maintain a balanced GM, particularly through diet and the use of probiotics, are being evaluated. Most recently, the effect of antihypertensive fermented milks on GM has been addressed. New evidence suggests that antihypertensive fermented milks may modulate GM. Thus, the aim of this review is to present available information related to the effect of antihypertensive fermented milks on gut microbiota.

Evaluation of acrylamide-removing properties of bacterial consortia under simulated gastrointestinal conditions.

BACKGROUND: Previous studies have demonstrated the acrylamide-removing properties of probiotic monocultures; however, potential advantages of consortia over monocultures in reducing the dietary exposure to acrylamide have not been proven. Hence this work aims to assess the acrylamide (AA)-binding properties of bacterial consortia, consisting of either probiotic strains and / or representative bacteria of duodenal microbiota, exposed to simulated gastrointestinal conditions (SGC). The AA binding capacity of ten probiotic strains (PS) and six duodenal strains (NDS) was evaluated under different conditions; then, three different consortia (PS, NDS, and PS + NDS) were assessed under SGC. RESULTS: Among individual PS, Bacillus coagulans GBI-30, Lactobacillus fermentum J23, L. pentosus J37 and J24, and L. casei Shirota, exhibited the highest AA-binding capacity (80-87%), while Bifidobacterium catenulatun ATCC27676, Streptococcus salivarius subsp. thermophilus ATCC19258, and S. gallolyticus ATCC9809 were the best (ca. 68%) NDS monocultures. Probiotic strain consortia showed higher (P < 0.05) AA binding capacity (> 90%) than monoculture bacteria. Conversely, individual NDS cultures displayed higher (P < 0.05) binding capacity than NDS consortia (60%). A significant reduction (P < 0.05) in AA removal capacity was observed when consortia were exposed to SGC, PS consortia being the most effective (> 60% removal). CONCLUSION: These results suggest that consortia of specific PS could play an important role in reducing the intestinal availability of acrylamide. © 2021 Society of Chemical Industry.

A detailed description of the CO molecule adsorbed in InOF-1.

CO is extremely toxic to humans since it can combine with haemoglobin to form carboxy-haemoglobin that reduces the oxygen-carrying capacity of blood. Metal-organic frameworks (MOFs), in particular InOF-1, are currently receiving preferential attention for the separation and capture of CO. In this investigation we report a theoretical study based on periodic density-functional-theory (DFT) analysis and matching experimental results (in situ DRIFTS). The aim of this article is to describe the non-covalent interactions between the functional groups of InOF-1 and the CO molecule since they are crucial to understand the adsorption mechanism of these materials. Our results show that the CO molecule mainly interacts with the µ2-OH hydroxo groups of InOF-1 through O-HO hydrogen bonds, and Cπ interactions by the biphenyl rings of the MOF. These results provide useful information on the CO adsorption mechanisms in InOF-1.

Fatal granulomatous amoebic encephalitis due to free-living amoebae in two boys in two different hospitals in Lima, Perú.

Granulomatous amoebic encephalitis caused by free-living amoebae is a rare condition that is difficult to diagnose and hard to treat, generally being fatal. Anti-amoebic treatment is often delayed because clinical signs and symptoms may hide the probable causing agent misleading the appropriate diagnostic test. There are four genera of free-living amoeba associated with human infection, Naegleria, Acanthamoeba sp., Balamuthia and Sappinia. Two boys were admitted with diagnosis of acute encephalitis. The history of having been in contact with swimming pools and rivers, supports the suspicion of an infection due to free-living amoebae. In both cases a brain biopsy was done, the histology confirmed granulomatous amoebic encephalitis with the presence of amoebic trophozoites.

Lipoxygenase and Its Relationship with Ethylene During Ripening of Genetically Modified Tomato (Solanum lycopersicum).

RESEARCH BACKGROUND: TomloxB is the main isoform of lipoxygenase associated with ripening and senescence of fruits. On the other hand, ethylene, a gaseous hormone, is essential for the regulation of ripening in climacteric fruits like tomatoes. However, the relationship between TomloxB and ethylene production has not been thoroughly studied. Therefore, we aim to assess the effect of exogenous ethylene in transgenic tomatoes that contain a silenced TomloxB gene, and subsequently evaluate lipoxygenase activity, 1-aminocyclopropane-1-carboxylic acid oxidase and ethylene production; as well as to quantify the expression of the genes encoding 1-aminocyclopropane-1-carboxylic acid oxidase and TomloxB. EXPERIMENTAL APPROACH: To investigate the effect of lipoxygenase and 1-aminocyclopropane-1-carboxylic acid oxidase activity, fruits harvested at the stages of break, turning and pink were used. Tomatoes at break stage collected from transgenic and wild type plants were used to determine ethylene production and gene expression. Genetically modified and wild type tomato fruits were exposed to 100 µL/L exogenous ethylene. Lipoxygenase activity was measured spectrophotometrically. Activity of 1-aminocyclopropane-1-carboxylic acid oxidase and ethylene production were determined by gas chromatography. Oligonucleotides for differentially expressed genes: 1-aminocyclopropane-1-carboxylic acid oxidase and TomloxB were used to determine gene expression by real-time PCR. RESULTS AND CONCLUSIONS: The data showed that silencing of TomloxB caused a reduction in lipoxygenase activity and ethylene production in tomato fruits, and also reduced 1-aminocyclopropane-1-carboxylic acid oxidase activity. Hence, the addition of exogenous ethylene increased lipoxygenase activity in all treatments and 1-aminocyclopropane-1-carboxylic acid oxidase activity only in transgenic lines at break stage, consequently there was a positive regulation between TomloxB and ethylene, as increasing the amount of ethylene increased the activity of lipoxygenase. The results suggest that lipoxygenase may be a regulator of 1-aminocyclopropane-1-carboxylic acid oxidase and production of ethylene at break stage. NOVELTY AND SCIENTIFIC CONTRIBUTION: These results lead to a better understanding of the metabolic contribution of TomloxB in fruit ripening and how it is linked to the senescence-related process, which can lead to a longer shelf life of fruits. Understanding this relationship between lipoxygenase and ethylene can be useful for better post-harvest handling of tomatoes.

Phenotypic similarity for rare disease: Ciliopathy diagnoses and subtyping.

Rare diseases are often hard and long to be diagnosed precisely, and most of them lack approved treatment. For some complex rare diseases, precision medicine approach is further required to stratify patients into homogeneous subgroups based on the clinical, biological or molecular features. In such situation, deep phenotyping of these patients and comparing their profiles based on subjacent similarities are thus essential to help fast and precise diagnoses and better understanding of pathophysiological processes in order to develop therapeutic solutions. In this article, we developed a new pipeline of using deep phenotyping to define patient similarity and applied it to ciliopathies, a group of rare and severe diseases caused by ciliary dysfunction. As a French national reference center for rare and undiagnosed diseases, the Necker-Enfants Malades Hospital (Necker Children's Hospital) hosts the Imagine Institute, a research institute focusing on genetic diseases. The clinical data warehouse contains on one hand EHR data, and on the other hand, clinical research data. The similarity metrics were computed on both data sources, and were evaluated with two tasks: diagnoses with EHRs and subtyping with ciliopathy specific research data. We obtained a precision of 0.767 in the top 30 most similar patients with diagnosed ciliopathies. Subtyping ciliopathy patients with phenotypic similarity showed concordances with expert knowledge. Similarity metrics applied to rare disease offer new perspectives in a translational context that may help to recruit patients for research, reduce the length of the diagnostic journey, and better understand the mechanisms of the disease.

Prostate cancer screening in low- and middle-income countries: the Mexican case.

Prostate-specific antigen (PSA)-based early detection for prostate cancer is the subject of intense debate. Implementation of organized prostate cancer screening has been challenging, in part because the PSA test is so amenable to opportunistic screening. To the extent that access to cancer screening tests increases in low- and middle-income countries (LMICs), there is an urgent need to thoughtfully evaluate existing and future cancer screening strategies to ensure benefit and control costs. We used Mexico's prostate cancer screening efforts to illustrate the challenges LMICs face. We provide five considerations for policymakers for a smarter approach and implementation of PSA-based screening.

El uso del Antígeno Prostático Específico (APE) para tamizaje para cáncer de próstata sigue siendo tema de amplio debate. La implementación de estrategias de tamiz organizado de cáncer de próstata ha sido un reto en parte porque la prueba de APE se presta para detección oportunista. A medida que aumenta el acceso a las pruebas de detección de cáncer en los países de ingresos bajos y medianos (PIBM), existe la necesidad urgente de evaluar cuidadosamente las estrategias actuales y futuras de detección oportuna de cáncer para garantizar su beneficio y controlar sus costos. Utilizamos los esfuerzos de tamizaje de cáncer de próstata de México para ilustrar los retos para PIBM. Ofrecemos cinco consideraciones dirigidas a tomadores de decisión que permitan contar con estrategias racionales de implementación de tamizaje para cáncer de próstata basado en el uso de APE.

Multiparametric magnetic resonance imaging-guided salvage radiotherapy in prostate cancer.

AIM: To analyse the efficacy and toxicity of postprostatectomy SRT in patients with a BCR evaluated with mpMRI. BACKGROUND: Multiparametric magnetic resonance imaging (mpMRI) has the ability to detect the site of pelvic recurrence in patients with biochemical recurrence (BCR) after radical prostatectomy (RP). However, we do not know the oncological outcomes of mpMRI-guided savage radiotherapy (SRT). RESULTS: Local, lymph node, and pelvic bone recurrence was observed in 13, 4 and 2 patients, respectively. PSA levels were significantly lower in patients with negative mpMRI (0.4 ng/mL [0.4]) vs. positive mpMRI (2.2 ng/mL [4.1], p = 0.003). Median planning target volume doses in patients with visible vs. non-visible recurrences were 76 Gy vs. 70 Gy. Overall, mean follow-up was 41 months (6-81). Biochemical relapse-free survival (bRFS) at 3 years was 82.3% and 82.5%, respectively, for the negative and positive mpMRI groups (p = 0.800). Three-year rates of late grade ≥2 urinary and rectal toxicity were 14.8% and 1.9%, respectively; all but one patient recovered without sequelae. CONCLUSION: SRT to the macroscopic recurrence identified by mpMRI is a feasible and well-tolerated option. In this study, there were no differences in bRFS between MRI-positive and MRI-negative patients, indicating effective targeting of MRI-positive lesions.

Smoking and prostate cancer: a life course analysis.

BACKGROUND: Inconsistent associations between smoking status and prostate cancer (PC) could be due to exposure assessment error. Reconstructing smoking behaviors over the life course could reduce exposure assessment error. METHODS: As part of a case-control study, we identified 402 incident and histologically confirmed PC cases that were matched by age (±5 years) to 805 population controls. Through direct interview, we obtained information about: age at smoking onset, intensity and frequency of cigarette smoking at different life stages, and smoking cessation age. Smoking status at interview and average smoking index over the lifetime (packs/year) were estimated. Life course smoking patterns were obtained applying the k-means+ method for longitudinal data to the smoking index (pack/year) for each life stage. RESULTS: Two life-course smoking patterns were identified among ever smokers: "pattern A" characterized by males who reported low and constant smoking intensity (87.8%), and "pattern B" (12.2%) males with an initial period of low intensity, followed by an increase during the second period. Compared to never smokers, pattern B was associated with higher poorly differentiated PC, (OR 2.30; 95% CI 1.21-4.38). No association was observed with average smoking index. CONCLUSION: Life course smoking patterns seem to capture the smoking variability during life course and reduce the likelihood of reverse causation. Using this assessment strategy our findings support the potential role of tobacco smoking in PC, particularly poorly differentiated PC. Prospective studies with comprehensive smoking history during the lifetime are needed to confirm these findings.

Increased Postharvest Life of TomLox B Silenced Mutants of Tomato (Solanum lycopersicum) Var. TA234.

A healthy lifestyle includes fruits and vegetables consumption. Tomato is one of the most consumed vegetables, although it is susceptible to physical damage through postharvest handling, thus leading to important losses. Softening is an important variable during tomato ripening; excessive softening is undesirable and leads to postharvest losses. TomloxB plays an important role in ripening, mainly in the loss of cellular integrity caused by fatty acids released from the lipid matrix of membranes that initiate oxidative deterioration, which is in turn carried into senescence. In order to increase postharvest life, we produced transgenic tomato plants via Rhizobium radiobacter with tomato lipoxygenase B (TomloxB) antisense constructs under control of the cauliflower mosaic virus (CaMV) 35S promoter. Lipoxygenase activity and firmness were measured in tomato fruit and the fatty acids profile was determined. Transgenic fruits were maintained for 40 days at room temperature in optimal conditions, whereas wild type fruits remained in similar conditions for only six days. Firmness in pink and red stages was significantly lower in wild type fruits than in two transgenic lines. Linolenic acid was the most important fatty acid consumed by lipoxygenase in both turning and pink stages of ripening. Lipoxygenase activity was smaller in transformed fruits in comparison with the wild type. These results suggest that silencing the TomloxB gene promoted significant changes in the physiology of transformed tomatoes, being the increase in postharvest life the most important.

Efficacy of Tamsulosin, Oxybutynin, and their combination in the control of double-j stent-related lower urinary tract symptoms.

INTRODUCTION AND OBJECTIVE: Indwelling double J ureteral stents are used routinely in the resolution of ureteral obstruction caused by different etiologies. Evaluation of urinary symptoms related to double-J stent, indicate that these affect 73-90% of patients. We conducted a prospective, randomized study, to evaluate the efficacy of tamsulosin, oxybutinin and combination therapy in improving the urinary symptoms. METHODS: Patients who underwent ureteral stent placement after ureterolithotripsy (total 51), were randomized into three groups: Group I: Tamsulosin 0.4 mg. Once per day(17 patients), Group II: Oxybutinin 5 mg. once per day (17 patients), Group III: Tamsulosin+ oxybutynin once per day (17 patients). All the groups received the drugs for three weeks and completed a Spanish validated Ureteral Stent Symptom Questionnaire (USSQ) at day 7 and 21. RESULTS: Repeated measures ANOVA showed mean urinary symptom index score was 22.3 vs. 15.5 in group three (p<0.001) at day 7 and 21 respectively. The mean work performance index was 6.6 vs 8.1 (p=0.049) favoring tamsulosin group, the mean sexual score was 0.5 vs 1.5 (p=0.03). Among additional problems the mean was 7.2 vs 6.2 (p=0.03). No significant difference was noted among pain and general health index. No side effects were reported. CONCLUSIONS: Combination therapy with tamsulosin and oxybutynin improved irritative symptoms and work performance as well as sexual matters. Combination therapy should be considered for patients who complained of stent related symptoms.

"Bind and Crawl" Association Mechanism of Leishmania major Peroxidase and Cytochrome c Revealed by Brownian and Molecular Dynamics Simulations.

Leishmania major, the parasitic causative agent of leishmaniasis, produces a heme peroxidase (LmP), which catalyzes the peroxidation of mitochondrial cytochrome c (LmCytc) for protection from reactive oxygen species produced by the host. The association of LmP and LmCytc, which is known from kinetics measurements to be very fast (∼10(8) M(-1) s(-1)), does not involve major conformational changes and has been suggested to be dominated by electrostatic interactions. We used Brownian dynamics simulations to investigate the mechanism of formation of the LmP-LmCytc complex. Our simulations confirm the importance of electrostatic interactions involving the negatively charged D211 residue at the LmP active site, and reveal a previously unrecognized role in complex formation for negatively charged residues in helix A of LmP. The crystal structure of the D211N mutant of LmP reported herein is essentially identical to that of wild-type LmP, reinforcing the notion that it is the loss of charge at the active site, and not a change in structure, that reduces the association rate of the D211N variant of LmP. The Brownian dynamics simulations further show that complex formation occurs via a "bind and crawl" mechanism, in which LmCytc first docks to a location on helix A that is far from the active site, forming an initial encounter complex, and then moves along helix A to the active site. An atomistic molecular dynamics simulation confirms the helix A binding site, and steady state activity assays and stopped-flow kinetics measurements confirm the role of helix A charges in the association mechanism.

Enzymatic Mechanism of Leishmania major Peroxidase and the Critical Role of Specific Ionic Interactions.

Leishmania major peroxidase (LmP) is very similar to the well-known yeast cytochrome c peroxidase (CcP). Both enzymes catalyze the peroxidation of cytochrome c. Like CcP, LmP reacts with H2O2 to form Compound I, which consists of a ferryl heme and a Trp radical, Fe(IV)═O;Trp(•+). Cytochrome c (Cytc) reduces the Trp radical to give Compound II, Fe(IV)═O;Trp, which is followed by an intramolecular electron transfer to give Fe(III)-OH;Trp(•+), and in the last step, Cytc reduces the Trp radical. In this study, we have used steady-state and single-turnover kinetics to improve our understanding of the overall mechanism of LmP catalysis. While the activity of CcP greatly increases with ionic strength, the kcat for LmP remains relatively constant at all ionic strengths tested. Therefore, unlike CcP, where dissociation of oxidized Cytc is limiting at low ionic strengths, association/dissociation reactions are not limiting at any ionic strength in LmP. We conclude that in LmP, the intramolecular electron transfer reaction, Fe(IV)═O;Trp to Fe(III)-OH;Trp(•+), is limiting at all ionic strengths. Unlike CcP, LmP depends on key intermolecular ion pairs to form the electron transfer competent complex. Mutating these sites causes the initial rate of association to decrease by 2 orders of magnitude and a substantial decrease in kcat. The drop in kcat is due to a switch in the rate-limiting step of the mutants from intramolecular electron transfer to the rate of association in forming the LmP-LmCytc complex. These studies show that while LmP and CcP form very similar complexes and exhibit similar activities, they substantially differ in how their activity changes as a function of ionic strength. This difference is primarily due to the heavy reliance of LmP on highly specific intermolecular ion pairs, while CcP relies mainly on nonpolar interactions.