Computational Insights into Prostaglandin E2 Ligand Binding and Activation of G-Protein-Coupled Receptors.

G-protein coupled receptors (GPCRs) are eukaryotic integral membrane proteins that regulate signal transduction cascade pathways implicated in a variety of human diseases and are consequently of interest as drug targets. For this reason, it is of interest to investigate the way in which specific ligands bind and trigger conformational changes in the receptor during activation and how this in turn modulates intracellular signaling. In the present study, we investigate the way in which the ligand Prostaglandin E2 interacts with three GPCRs in the E-prostanoid family: EP1, EP2, and EP3. We examine information transfer pathways based on long-time scale molecular dynamics simulations using transfer entropy and betweenness centrality to measure the physical transfer of information among residues in the system. We monitor specific residues involved in binding to the ligand and investigate how the information transfer behavior of these residues changes upon ligand binding. Our results provide key insights that enable a deeper understanding of EP activation and signal transduction functioning pathways at the molecular level, as well as enabling us to make some predictions about the activation pathway for the EP1 receptor, for which little structural information is currently available. Our results should advance ongoing efforts in the development of potential therapeutics targeting these receptors.

Alterations in gut microbiota linked to provenance, sex, and chronic wasting disease in white-tailed deer (Odocoileus virginianus).

Chronic wasting disease (CWD) is a fatal, contagious, neurodegenerative prion disease affecting both free-ranging and captive cervid species. CWD is spread via direct or indirect contact or oral ingestion of prions. In the gastrointestinal tract, prions enter the body through microfold cells (M-cells), and the abundance of these cells can be influenced by the gut microbiota. To explore potential links between the gut microbiota and CWD, we collected fecal samples from farmed and free-ranging white-tailed deer (Odocoileus virginianus) around the Midwest, USA. Farmed deer originated from farms that were depopulated due to CWD. Free-ranging deer were sampled during annual deer harvests. All farmed deer were tested for CWD via ELISA and IHC, and we used 16S rRNA gene sequencing to characterize the gut microbiota. We report significant differences in gut microbiota by provenance (Farm 1, Farm 2, Free-ranging), sex, and CWD status. CWD-positive deer from Farm 1 and 2 had increased abundances of Akkermansia, Lachnospireacea UCG-010, and RF39 taxa. Overall, differences by provenance and sex appear to be driven by diet, while differences by CWD status may be linked to CWD pathogenesis.

Calculating Transfer Entropy from Variance-Covariance Matrices Provides Insight into Allosteric Communication in ERK2.

We develop an approach by which reliable estimates of the transfer entropy can be obtained from the variance-covariance matrix of atomic fluctuations, which converges quickly and retains sensitivity to the full chemical profile of the biomolecular system. We validate our method on ERK2, a well-studied kinase involved in the MAPK signaling cascade for which considerable computational, experimental, and mutation data are available. We present the results of transfer entropy analysis on data obtained from molecular dynamics simulations of wild-type active and inactive ERK2, along with mutants Q103A, I84A, L73P, and G83A. We show that our method is systematically consistent within the context of other approaches for calculating transfer entropy, and we provide a method for interpreting networks of interconnected residues in the protein from a perspective of allosteric coupling. We introduce new insights about possible allosteric activity of the extreme N-terminal region of the kinase, and we describe evidence that suggests that activation may occur by different paths or routes in different mutants. Our results highlight systematic advantages and disadvantages of each method for calculating transfer entropy and show the important role of transfer entropy analysis for understanding allosteric behavior in biomolecular systems.

Multivariate mortality analyses in COVID-19: Comparing patients with cancer and patients without cancer in Louisiana.

BACKGROUND: This is the largest and only multivariate study evaluating the difference in mortality from coronavirus disease 2019 (COVID-19) between patients with cancer and patients without cancer in the United States. The objective was to assess COVID-19 mortality rates in patients with cancer versus patients without cancer and uncover possible statistically significant characteristics contributing to mortality. METHODS: This retrospective study analyzed patients with cancer and patients without cancer who tested positive for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) from March 1 through April 30, 2020. This was a multicenter study in the state of Louisiana throughout the Ochsner Health System in both tertiary and nontertiary centers. Patients older than 18 years were eligible. Three hundred twelve patients with cancer were compared with 4833 patients without cancer. RESULTS: Mortality was found to be higher in the cancer group. Patients of advanced age with cancer had a significant increase in mortality (odds ratio [OR], 5.96; P < .001). Other significant risk factors for increased mortality were male sex (OR, 2.15), a history of chronic kidney disease (OR, 3.84), and obesity (OR, 1.30). In hospitalized patients with cancer, adverse vital signs on admission, decreased absolute lymphocyte counts, thrombocytopenia, elevated creatinine, lactic acidosis, and elevated procalcitonin all seemed to increase the risk of death. Among patients with cancer, active or progressive disease (P < .001) and recent therapy (OR, 2.34; 95% confidence interval, 1.08-5.08) were shown to increase mortality. CONCLUSIONS: Patients with cancer have increased mortality in the setting of infection with SARS-CoV-2 in comparison with patients without cancer. Patients with cancer who are 65 years of age or older and those with certain comorbidities have the greatest risk of death. Recent cancer-directed therapy and disease status also seem to play roles in mortality. LAY SUMMARY: This is the largest study of patients with cancer versus patients without cancer to date and is the first multivariate analysis study comparing these 2 patient populations. This study confirms the hypothesis that patients with cancer are at increased risk for mortality and that there are multiple characteristics posing the potential to risk-stratify these patients in the setting of a future outbreak.

Synthetic flavonoid derivatives targeting the glycogen phosphorylase inhibitor site: QM/MM-PBSA motivated synthesis of substituted 5,7-dihydroxyflavones, crystallography, in vitro kinetics and ex-vivo cellular experiments reveal novel potent inhibitors.

Glycogen phosphorylase (GP) is an important target for the development of new anti-hyperglycaemic agents. Flavonoids are novel inhibitors of GP, but their mode of action is unspecific in terms of the GP binding sites involved. Towards design of synthetic flavonoid analogues acting specifically at the inhibitor site and to exploit the site's hydrophobic pocket, chrysin has been employed as a lead compound for the in silico screening of 1169 new analogues with different B ring substitutions. QM/MM-PBSA binding free energy calculations guided the final selection of eight compounds, subsequently synthesised using a Baker-Venkataraman rearrangement-cyclisation approach. Kinetics experiments against rabbit muscle GPa and GPb together with human liver GPa, revealed three of these compounds (11, 20 and 43) among the most potent that bind at the site (Ki s < 4 µM for all three isoforms), and more potent than previously reported natural flavonoid inhibitors. Multiple inhibition studies revealed binding exclusively at the inhibitor site. The binding is synergistic with glucose suggesting that inhibition could be regulated by blood glucose levels and would decrease as normoglycaemia is achieved. Compound 43 was an effective inhibitor of glycogenolysis in hepatocytes (IC50 = 70 µM), further promoting these compounds for optimization of their drug-like potential. X-ray crystallography studies revealed the B-ring interactions responsible for the observed potencies.

Identification, clinical manifestation and structural mechanisms of mutations in AMPK associated cardiac glycogen storage disease.

BACKGROUND: Although 21 causative mutations have been associated with PRKAG2 syndrome, our understanding of the syndrome remains incomplete. The aim of this project is to further investigate its unique genetic background, clinical manifestations, and underlying structural changes. METHODS: We recruited 885 hypertrophic cardiomyopathy (HCM) probands and their families internationally. Targeted next-generation sequencing of sudden cardiac death (SCD) genes was performed. The role of the identified variants was assessed using histological techniques and computational modeling. FINDINGS: Twelve PRKAG2 syndrome kindreds harboring 5 distinct variants were identified. The clinical penetrance of 25 carriers was 100.0%. Twenty-two family members died of SCD or heart failure (HF). All probands developed bradycardia (HRmin, 36.3 ±â€¯9.8 bpm) and cardiac conduction defects, and 33% had evidence of atrial fibrillation/paroxysmal supraventricular tachycardia (PSVT) and 67% had ventricular preexcitation, respectively. Some carriers presented with apical hypertrophy, hypertension, hyperlipidemia, and renal insufficiency. Histological study revealed reduced AMPK activity and major cardiac channels in the heart tissue with K485E mutation. Computational modelling suggests that K485E disrupts the salt bridge connecting the ß and γ subunits of AMPK, R302Q/P decreases the binding affinity for ATP, T400N and H401D alter the orientation of H383 and R531 residues, thus altering nucleotide binding, and N488I and L341S lead to structural instability in the Bateman domain, which disrupts the intramolecular regulation. INTERPRETATION: Including 4 families with 3 new mutations, we describe a cohort of 12 kindreds with PRKAG2 syndrome with novel pathogenic mechanisms by computational modelling. Severe clinical cardiac phenotypes may be developed, including HF, requiring close follow-up.

First meeting in Asia of the Asia Pacific Research Integrity network.

In 2017, the University of Hong Kong and the University of California San Diego co-hosted the first Asian meeting of the recently formed Asia Pacific Research Integrity (APRI) network in Hong Kong. Aligned with planning meetings in 2015 and 2016 funded in part by the US Office of Research Integrity (ORI), the Hong Kong meeting was designed by a multi-national planning committee to address pressing challenges in research integrity: improving multi-national communication; exchanging information on managing misconduct investigations; and sharing best practices to promote research integrity. To create a sustainable, robust international partnership to promote research integrity in the region, the purpose of this 2017 meeting was to foster multi-national awareness, understanding, and opportunities for collaboration. The meeting was defined by four objectives that emerged from the previous meetings: (1) Articulate differences as well as areas of common ground; (2) Identify best or recommended practices; (3) Identify opportunities for research or collaboration; and (4) Set an APRI network agenda for coming years. The key anticipated outcome was to advance the conversation surrounding research integrity among academic institutions and regulators in Asian and Pacific Rim nations. This outcome was evidenced by meeting participation, participant satisfaction, and articulation of next steps for the APRI network.

The Cancer Care Index: A Novel Metric to Assess Overall Performance of a Pediatric Oncology Program.

OBJECTIVE: Childhood cancer metrics are currently primarily focused on survival rates and late effects of therapy. Our objectives were to design and test a metric that reflected overall quality and safety performance, across all cancer types, of an oncology-bone marrow transplant service line and to use the metric to drive improvement. METHOD: The Cancer Care Index (CCI) aggregates adverse safety events and missed opportunities for best practices into a composite score that reflects overall program performance without regard to cancer type or patient outcome. Fifteen domains were selected in 3 areas as follows: (1) treatment-related quality and safety, (2) provision of a harm-free environment, and (3) psychosocial support. The CCI is the aggregate number of adverse events or missed opportunities to provide quality care in a given time frame. A lower CCI reflects better care and improved overall system performance. Multidisciplinary microsystem-based teams addressed specific aims for each domain. The CCI was widely followed by all team members, particularly frontline providers. RESULTS: The CCI was easy to calculate and deploy and well accepted by the staff. The annual CCI progressively decreased from 278 in 2012 to 160 in 2014, a 42% reduction. Improvements in care were realized across most index domains. Multiple new initiatives were successfully implemented. CONCLUSIONS: The CCI is a useful metric to document performance improvement across a broad range of domains, regardless of cancer type. By the use of quality improvement science, progressive reduction in CCI has occurred over a 3-year period.

Identification of C-ß-d-Glucopyranosyl Azole-Type Inhibitors of Glycogen Phosphorylase That Reduce Glycogenolysis in Hepatocytes: In Silico Design, Synthesis, in Vitro Kinetics, and ex Vivo Studies.

Several C-ß-d-glucopyranosyl azoles have recently been uncovered as among the most potent glycogen phosphorylase (GP) catalytic site inhibitors discovered to date. Toward further exploring their translational potential, ex vivo experiments have been performed for their effectiveness in reduction of glycogenolysis in hepatocytes. New compounds for these experiments were predicted in silico where, for the first time, effective ranking of GP catalytic site inhibitor potencies using the molecular mechanics-generalized Born surface area (MM-GBSA) method has been demonstrated. For a congeneric training set of 27 ligands, excellent statistics in terms of Pearson (RP) and Spearman (RS) correlations (both 0.98), predictive index (PI = 0.99), and area under the receiver operating characteristic curve (AU-ROC = 0.99) for predicted versus experimental binding affinities were obtained, with ligand tautomeric/ionization states additionally considered using density functional theory (DFT). Seven 2-aryl-4(5)-(ß-d-glucopyranosyl)-imidazoles and 2-aryl-4-(ß-d-glucopyranosyl)-thiazoles were subsequently synthesized, and kinetics experiments against rabbit muscle GPb revealed new potent inhibitors with best Ki values in the low micromolar range (5c = 1.97 µM; 13b = 4.58 µM). Ten C-ß-d-glucopyranosyl azoles were then tested ex vivo in mouse primary hepatocytes. Four of these (5a-c and 9d) demonstrated significant reduction of glucagon stimulated glycogenolysis (IC50 = 30-60 µM). Structural and predicted physicochemical properties associated with their effectiveness were analyzed with permeability related parameters identified as crucial factors. The most effective ligand series 5 contained an imidazole ring, and the calculated pKa (Epik: 6.2; Jaguar 5.5) for protonated imidazole suggests that cellular permeation through the neutral state is favored, while within the cell, there is predicted more favorable binding to GP in the protonated form.

An Introductory, Computer-Based Learning Module for Interpreting Noncontrast Head Computed Tomography.

Introduction: New radiology and other residents must quickly assimilate a vast amount of anatomic and pathologic information when learning to interpret noncontrast head computed tomography (CT). No interactive, computer-based module using a search-pattern approach to provide new residents with the groundwork for interpretation of noncontrast head CT previously existed. Methods: We developed such a learning module using PowerPoint. First-year radiology residents completed the module prior to their neuroradiology rotation, and neurology residents completed it during orientation. Residents took 20-question pre- and posttests to assess knowledge and a postmodule survey. Each resident was randomized to one of two pretests and took the opposite as the posttest. Scores were collected over 5 years for radiology residents and 4 years for neurology residents. Statistical analysis of scores was performed using t tests. Results: Forty-seven first-year radiology residents and 31 neurology residents completed the module and the pre- and posttests. Scores for all residents either stayed the same or increased, regardless of the order of the versions of the pre- or posttests; the mean score increase was 4 (p < .0001) out of 20. Radiology residents had higher mean scores than neurology residents on the pre- and posttests, which were statistically significant (p < .04 and .0004, respectively). Feedback on the survey was overwhelmingly positive. Discussion: This computerized learning module is effective for teaching basic interpretation skills to new radiology and neurology residents. The module allows for asynchronous, programmed learning and the use of a step-by-step search-pattern approach.

Benefits of a resident-run orientation for new radiology trainees.

Incoming radiology residents must rapidly assimilate large amounts of technical, medical, and operational information. This can be overwhelming and contribute to anxiety. Typical introductory curricula focused on radiologic content may not address the concerns of new residents. Two consecutive classes of incoming radiology residents participated in our study. For groups A (n=11) and B (n=11), the existing introductory lectures were given by faculty. For group B, residents hosted sessions for each rotation, including round-table discussions and work area tours, with emphasis on resident roles, personnel, and workflow. With institutional review board exemption, residents were anonymously surveyed before and after the sessions regarding: awareness of responsibilities, familiarity with anatomy, and anxiety regarding each rotation on a 1-4 scale. Free-text comments were collected. Comparison was performed using Wilcoxon rank sum test. Group A reported increased role awareness (P=0.04), greater content familiarity (P<0.05), and decreased anxiety (P=0.02) in one rotation each. There were 3 of 12 rotations in group B that showed significantly increased role awareness (P range <0.01 to 0.01) and decreased anxiety (P range <0.01 to <0.05). In addition, two rotations indicated improved role awareness only (P=0.02 and P=0.04), while there were four rotations reported decreased anxiety only (P range 0.01 to 0.03). Free-text commenters preferred the resident-run portions of the sessions. In conclusion, adding role-oriented introductory sessions to existing lectures for first-year residents decreased anxiety and increased role awareness for all rotations; therefore, it is suggested that anxiety may be better addressed by role-oriented content, and resident-to-resident teaching may have benefits.

Imaging techniques for the diagnosis of hepatocellular carcinoma and the evaluation of response to treatment.

Imaging plays a critical role in the diagnosis of hepatocellular carcinoma (HCC). In the USA, non-invasive imaging based diagnosis of HCC has largely replaced biopsy because of the high specificity and positive predictive value of imaging features for HCC. Because of the important role of imaging and the need to promote standardization of the management of HCC, several imaging-based algorithms for the diagnosis of HCC in at-risk patients have been developed.Imaging also plays a vital role in the assessment of HCC response to locoregional therapies (LRT) such as ablative and endovascular therapies. Standard imaging response criteria of solid tumors that rely solely on change in tumor size for determination of therapeutic success are not applicable to HCC undergoing LRT. Therefore, several systems have been developed over the years to objectively evaluate HCC response to LRT.In this review, we will describe major and ancillary imaging features of HCC, how these features are incorporated into the various imaging based algorithms, discuss the differences between algorithms, and address the emerging role of new imaging techniques and contrast agents in the diagnosis of HCC. We will also discuss the importance of assessment of HCC response to LRT, describe patterns of imaging response to the various therapies including newer volumetric and functional response measures, and examine and compare proposed response criteria of HCC to LRT.

Truncated variants of the GCN4 transcription activator protein bind DNA with dramatically different dynamical motifs.

The yeast protein GCN4 is a transcriptional activator in the basic leucine zipper (bZip) family, whose distinguishing feature is the "chopstick-like" homodimer of alpha helices formed at the DNA-binding interface. While experiments have shown that truncated versions of the protein retain biologically relevant DNA-binding affinity, we present the results of a computational study revealing that these variants show a wide variety of dynamical modes in their interaction with the target DNA sequence. We have performed all-atom molecular dynamics simulations of the full-length GCN4 protein as well as three truncated variants; our data indicate that the truncated mutants show dramatically different correlation patterns. We conclude that although the truncated mutants still retain DNA-binding ability, the bZip interface present in the full-length protein provides important stability for the protein-DNA complex.

MR imaging in cirrhosis and hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) is the fastest growing cause of cancer-related death in the United States. Cirrhosis is the most important risk factor for HCC. Dynamic contrast-enhanced magnetic resonance (MR) imaging is the modality of choice for working up nodules detected at screening, for staging known HCC, and for follow-up. In cirrhotic livers, the combination of tumor arterial phase hyperenhancement plus washout and/or capsular enhancement is highly specific for HCC and can make biopsy unnecessary. Newer imaging techniques may further improve MR imaging sensitivity for HCC and help to characterize tumors with atypical dynamic enhancement patterns.

Magnetic resonance imaging in cirrhosis: what's new?

Cirrhosis is the main risk factor for the development of hepatocellular carcinoma (HCC). The major causative factors of cirrhosis in the United States and Europe are chronic hepatitis C infection and excessive alcohol consumption with nonalcoholic steatohepatitis emerging as another important risk factor. Magnetic resonance imaging is the most sensitive imaging technique for the diagnosis of HCC, and the sensitivity can be further improved with the use of diffusion-weighted imaging and hepatocyte-specific contrast agents. The combination of arterial phase hyperenhancement, venous or delayed phase hypointensity "washout feature," and capsular enhancement are features highly specific for HCC with reported specificities of 96% and higher. When these features are present in a mass in the cirrhotic liver, confirmatory biopsy to establish the diagnosis of HCC is not necessary. Other tumors, such as cholangiocarcinoma, sometimes occur in the cirrhotic at a much lower rate than HCC and can mimic HCC, as do other benign lesions such as perfusion abnormalities. In this article, we discuss the imaging features of cirrhosis and HCC, the role of magnetic resonance imaging in the diagnosis of HCC and other benign and malignant lesions that occur in the cirrhotic liver, and the issue of nonspecific arterially hyperenhancing nodules often seen in cirrhosis.

Identification of a novel de novo mutation associated with PRKAG2 cardiac syndrome and early onset of heart failure.

INTRODUCTION: The major structure elements of the AMP-activated protein kinase (AMPK) are α, ß, and γ sunbunits. Mutations in γ2 subunit (PRKAG2) have been associated with a cardiac syndrome including inherited ventricular preexcitation, conduction disorder and hypertrophy mimicking hypertrophic cardiomyopathy. The aim of the present study was to identify PRKAG2 syndrome among patients presenting with left ventricular hypertrophy (LVH). METHODS AND RESULTS: Nineteen unrelated subjects with unexplained LVH were clinically and genetically evaluated. Among 4 patients with bradycardia, manifestations of preexcitation were only found in a 19 year old male who also developed congestive heart failure 3 years later. Electrophysiological study of this case identified the coexistence of an AV accessory pathway and AV conduction defect. Histological analysis of his ventricular tissue isolated by biopsy confirmed excessive glycogen accumulation, prominent myofibrillar disarray and interstitial fibrosis. Direct sequencing of his DNA revealed a heterozygous mutation in PRKAG2 consisting of an A-to-G transition at nucleotide 1453 (c.1453A>G), predicting a substitution of a glutamic acid for lysine at highly-conserved residue 485 (p.Lys485Glu, K485E), which was absent in his unaffected family members and in 215 healthy controls. To assess the role of K485 in the structure and function of the protein, computational modeling calculations and conservation analyses were performed. Electrostatic calculations indicate that K485 forms a salt bridge with the conserved D248 residue in the AMPK ß subunit, which is critical for proper regulation of the enzyme, and the K485E mutant disrupts the connection. CONCLUSIONS: Our study identifies a novel de novo PRKAG2 mutation in a young, in which progression of the disease warrants close medical attention. It also underlines the importance of molecular screening of PRKAG2 gene in patients with unexplained LVH, ventricular preexcitation, conduction defect, and/or early onset of heart failure.

The natural DNA bending angle in the lac repressor headpiece-O1 operator complex is determined by protein-DNA contacts and water release.

We performed molecular dynamics simulations of the lac repressor headpiece-O1 operator complex for natural, over and underbent DNA to assess the factors that determine the natural DNA bending angle. At the natural angle, the specific and nonspecific contacts between the protein and DNA are optimized. Protein-DNA contacts show different angle dependences in the right and left sites, with the left site generally getting weaker and the right site getting stronger as the bending angle increases. Two entropic factors were identified as well: at the natural bending angle, water release and the quasiharmonic protein configurational entropy are maximized. The gain in protein configurational entropy might stem from an entropy-entropy compensation mechanism, in which a reduction in protein fluctuations is offset by a loss in correlations between the right and left sites.

Defining scholarly activity in graduate medical education.

BACKGROUND: Scholarly activity is a requirement for accreditation by the Accreditation Council for Graduate Medical Education. There is currently no uniform definition used by all Residency Review Committees (RRCs). A total of 6 of the 27 RRCs currently have a rubric or draft of a rubric to evaluate scholarly activity. OBJECTIVE: To develop a definition of scholarly activity and a set of rubrics to be used in program accreditation to reduce subjectivity of the evaluation of scholarly activity at the level of individual residency programs and across RRCs. METHODS: We performed a review of the pertinent literature and selected faculty promotion criteria across the United States to develop a structure for a proposed rubric of scholarly activity, drawing on work on scholarship by experts to create a definition of scholarly activity and rubrics for its assessment. RESULTS: The literature review showed that academic institutions in the United States place emphasis on all 4 major components of Boyer's definition of scholarship: discovery, integration, application, and teaching. We feel that the assessment of scholarly activity should mirror these findings as set forth in our proposed rubric. Our proposed rubric is intended to ensure a more objective evaluation of these components of scholarship in accreditation reviews, and to address both expectations for scholarly pursuits for core teaching faculty and those for resident and fellow physicians. CONCLUSION: The aim of our proposed rubric is to ensure a more objective evaluation of these components of scholarship in accreditation reviews, and to address expectations for scholarly pursuits for core teaching faculty as well as those for resident and fellow physicians.

Importance of domain closure for the autoactivation of ERK2.

Extracellular signal-regulated kinases 1 and 2 (ERK1 and -2, respectively) play a critical role in regulating cell division and have been implicated in cancer. In addition to activation by MAPK/ERK kinases 1 and 2 (MEK1 and -2, respectively), certain mutants of ERK2 can be activated by autophosphorylation. To identify the mechanism of autoactivation, we have performed a series of molecular dynamics simulations of ERK1 and -2 in various stages of activation as well as the constitutively active Q103A, I84A, L73P, and R65S ERK2 mutants. Our simulations indicate the importance of domain closure for autoactivation and activity regulation, with that event occurring prior to folding of the activation lip and of loop L16. Results indicate that the second phosphorylation event, that of T183, disrupts hydrogen bonding involving D334, thereby allowing the kinase to lock into the active conformation. On the basis of the simulations, three predictions were made. G83A was suggested to impede activation; K162M was suggested to perturb the interface between the N- and C-domains leading to activation, and Q64C was hypothesized to stop folding of loop L16, thereby perturbing the homodimerization interface. Functional analysis of the mutants validated the predictions concerning the G83A and Q64C mutants. The K162M mutant did not autoactivate as predicted, however, which may be due to the location of the residue on the protein surface near the ED substrate docking domain.