Structural studies of human mitochondrial LonP1 and cytosolic prefoldin involved in protein homeostasis

The mitochondrial Lon protease homolog (LonP1) hexamer controls mitochondrial health by digesting proteins from the mitochondrial matrix that are damaged or must be removed. Understanding how it is regulated requires characterizing its mechanism. Here, we show how human LonP1 functions, based on eight different conformational states that we determined by cryo-EM with a resolution locally extending to 3.6 Å for the best ordered states. LonP1 has a poorly ordered N-terminal part with apparent threefold symmetry, which apparently binds substrate protein and feeds it into its AAA+ unfoldase core. This translocates the extended substrate protein into a proteolytic cavity, in which we report an additional, previously unidentified Thr-type proteolytic center. Threefold rocking movements of the flexible N-terminal assembly likely assist thermal unfolding of the substrate protein. Our data suggest LonP1 may function as a sixfold cyclical Brownian ratchet controlled by ATP hydrolysis

Statical Analysis of Rainfall for Development of Intensity-Duration-Frequency Curves for Upper Cauvery Karnataka by Log-Normal Distribution

Intensity–duration–frequency (IDF) curves are among the most demandable information in meteorology, hydrology and engineering water resources design, planning, operation, and management works. The IDF Curves accessible are for the most part done by fitting arrangement of yearly greatest precipitation force to parametric dispersions. Intensity-durationfrequency (IDF) curves represent the relationship between storm intensity, storm duration and return period. Environmental change is relied upon to intensify the boundaries in the atmosphere factors. Being prone to harsh climate impacts, it is very crucial to study extreme rainfall-induced flooding for short durations over regions that are rapidly growing. One way to approach the extremes is by the application of the Intensity-Duration-Frequency (IDF) curves. The annual maximum rainfall intensity (AMRI) characteristics are often used to construct these IDF curves that are being used in several infrastructure designs for urban areas. Thus, there is a necessity to obtain high temporal and spatial resolution rainfall information. Many urban areas of developing countries lack long records of short-duration rainfall. The shortest duration obtained is normally at a daily scale/24 h. This paper suggests their generation based on annual daily maximum rainfall (ADMR) records. Rainfall data of 23 (Twenty three) hydrological years of all stations were used. Maximum rainfall frequency analysis was made by LogNormal Distribution method

Structural basis of adenylyl cyclase 9 activation

Adenylyl cyclase 9 (AC9) is a membrane-bound enzyme that converts ATP into cAMP. The enzyme is weakly activated by forskolin, fully activated by the G protein Gαs subunit and is autoinhibited by the AC9 C-terminus. Although our recent structural studies of the AC9-Gαs complex provided the framework for understanding AC9 autoinhibition, the conformational changes that AC9 undergoes in response to activator binding remains poorly understood. Here, we present the cryo-EM structures of AC9 in several distinct states: (i) AC9 bound to a nucleotide inhibitor MANT-GTP, (ii) bound to an artificial activator (DARPin C4) and MANT-GTP, (iii) bound to DARPin C4 and a nucleotide analogue ATPαS, (iv) bound to Gαs and MANT-GTP. The artificial activator DARPin C4 partially activates AC9 by binding at a site that overlaps with the Gαs binding site. Together with the previously observed occluded and forskolin-bound conformations, structural comparisons of AC9 in the four conformations described here show that secondary structure rearrangements in the region surrounding the forskolin binding site are essential for AC9 activation

Structural basis of adenylyl cyclase 9 activation

Adenylyl cyclase 9 (AC9) is a membrane-bound enzyme that converts ATP into cAMP. The enzyme is weakly activated by forskolin, fully activated by the G protein Gαs subunit and is autoinhibited by the AC9 C-terminus. Although our recent structural studies of the AC9-Gαs complex provided the framework for understanding AC9 autoinhibition, the conformational changes that AC9 undergoes in response to activator binding remains poorly understood. Here, we present the cryo-EM structures of AC9 in several distinct states: (i) AC9 bound to a nucleotide inhibitor MANT-GTP, (ii) bound to an artificial activator (DARPin C4) and MANT-GTP, (iii) bound to DARPin C4 and a nucleotide analogue ATPαS, (iv) bound to Gαs and MANT-GTP. The artificial activator DARPin C4 partially activates AC9 by binding at a site that overlaps with the Gαs binding site. Together with the previously observed occluded and forskolin-bound conformations, structural comparisons of AC9 in the four conformations described here show that secondary structure rearrangements in the region surrounding the forskolin binding site are essential for AC9 activation

Predictors of Long-Term Survival After Hip Fractures-A 5 Year Results of A Retrospective Study

Purpose: The most important fractures in this setting are hip fractures. The mortality declines during the following years after surgery. There are different studies with contrary conclusions regarding the long term mortality. Only little is known about predictable characteristics regarding the 5-year mortality. Furthermore, the already existing data present inconsistent results. In order to identify the risk factors and predictors on long term survival this study was conducted in elderly patients with hip fracture.Methodology: The study is a Retrospective study. Patients aged above 60 years with fracture around hip in the year 2015 & 2016 was taken and analysed. The details of the patients are derived from MRD and patients are contacted through telephonic communication to find out the survival. We have excluded patients with age less than 60yrs, multiple fractures and malignancy related fractures. Parameters like age, sex, comorbidities, the day of presentation to hospital following fracture, hospital stay, whether patient was put on antiplatelets following surgery, years of survival after surgery or treated non operatively.Results: A total of 150 patients attended to our Yenepoya Medical College during 2015 and 2016 were included in study and evaluated. The mortality was more than 40 % in less than two years after fracture. In the multivariate analysis, significant risk factors for dying were male gender (p = 0.188), comorbidities (p = 0.860), antiplatelet following surgery (p = 0.015), presenting to hospital after fracture (p = 0.003), operating day following admission (p = 0.033), dearranged blood markers (p = 0.020).Conclusion: Our results confirms poor results after hip fracture in elderly population. While better results might be influenced by optimal fracture care, patient’s age, gender,day of presentation to hospital, day of undergoing surgery following admission, antiplatelet following surgery, dearranged blood markers before surgery. More prospective clinical studies are required to exactly predict the factors responsible for survival after fractures in elderly

Catalytic cycling of human mitochondrial Lon protease

The mitochondrial Lon protease (LonP1) regulates mitochondrial health by removing redundant proteins from the mitochondrial matrix. We determined LonP1 in eight nucleotide-dependent conformational states by cryoelectron microscopy (cryo-EM). The flexible assembly of N-terminal domains had 3-fold symmetry, and its orientation depended on the conformational state. We show that a conserved structural motif around T803 with a high similarity to the trypsin catalytic triad is essential for proteolysis. We show that LonP1 is not regulated by redox potential, despite the presence of two conserved cysteines at disulfide-bonding distance in its unfoldase core. Our data indicate how sequential ATP hydrolysis controls substrate protein translocation in a 6-fold binding change mechanism. Substrate protein translocation, rather than ATP hydrolysis, is a rate-limiting step, suggesting that LonP1 is a Brownian ratchet with ATP hydrolysis preventing translocation reversal. 3-fold rocking motions of the flexible N-domain assembly may assist thermal unfolding of the substrate protein

Endogenous Polyamines Reduce the Toxicity of Soluble Aβ Peptide Aggregates Associated with Alzheimer’s Disease

Polyamines promote the formation of the Aβ peptide amyloid fibers that are a hallmark of Alzheimer’s disease. Here we show that polyamines interact with nonaggregated Aβ peptides, thereby reducing the peptide’s hydrophobic surface. We characterized the associated conformational change through NMR titrations and molecular dynamics simulations. We found that even low concentrations of spermine, sperimidine, and putrescine fully protected SH-SY5Y (a neuronal cell model) against the most toxic conformational species of Aβ, even at an Aβ oligomer concentration that would otherwise kill half of the cells or even more. These observations lead us to conclude that polyamines interfere with the more toxic prefibrillar conformations and might protect cells by promoting the structural transition of Aβ toward its less toxic fibrillar state that we reported previously. Since polyamines are present in brain fluid at the concentrations where we observed all these effects, their activity needs to be taken into account in understanding the molecular processes related to the development of Alzheimer’s disease

Structural basis of adenylyl cyclase 9 activation

Adenylyl cyclase 9 (AC9) is a membrane-bound enzyme that converts ATP into cAMP. The enzyme is weakly activated by forskolin, fully activated by the G protein Gαs subunit and is autoinhibited by the AC9 C-terminus. Although our recent structural studies of the AC9-Gαs complex provided the framework for understanding AC9 autoinhibition, the conformational changes that AC9 undergoes in response to activator binding remains poorly understood. Here, we present the cryo-EM structures of AC9 in several distinct states: (i) AC9 bound to a nucleotide inhibitor MANT-GTP, (ii) bound to an artificial activator (DARPin C4) and MANT-GTP, (iii) bound to DARPin C4 and a nucleotide analogue ATPαS, (iv) bound to Gαs and MANT-GTP. The artificial activator DARPin C4 partially activates AC9 by binding at a site that overlaps with the Gαs binding site. Together with the previously observed occluded and forskolin-bound conformations, structural comparisons of AC9 in the four conformations described here show that secondary structure rearrangements in the region surrounding the forskolin binding site are essential for AC9 activation.ISSN:2041-172