Biology subjects

Goluguri, R. R.

Publications and source records attributed to Goluguri, R. R..

4 recordsLinked to original sources

bioRxiv2025

The G256E HCM mutation prolongs relaxation via altered nucleotide handling

Mutations in myosin alter its motor functions in diverse ways by affecting different structural and chemo-mechanical events. Multidisciplinary strategies can be used to understand how varying alterations in motor function converge to common phenotypes like hypercontractility and hypertrophic cardiomyopathy (HCM). Here, we combined molecular dynamics (MD) simulations with protein biochemical and myofibril mechanical analyses to study the HCM-causing myosin variant G256E. MD simulations demonstrated that G256E induces structural changes that increase the work required to displace ADP.Mg2+ from actomysoin complex. Stopped-flow biochemical analysis demonstrated increased ADP affinity for actomyosin and single myofibril mechanics analysis demonstrated increased force generation and reduced ADP sensitivity of the early, slow phase of relaxation. Together, these results demonstrate that slower ADP release from myosin during contraction is a significant contributor to pathological contractile nature of the G256E mutation. This study highlights the importance of detailed chemo-mechanical analysis of mutations associated with hereditary cardiac diseases.

biophysics↗

bioRxiv2024

A FRET assay to quantitate levels of the human β-cardiac myosin interacting heads motif based on its near-atomic resolution structure

In cardiac muscle, many myosin molecules are in a resting or "OFF" state with their catalytic heads in a folded structure known as the interacting heads motif (IHM). Many mutations in the human {beta}-cardiac myosin gene that cause hypertrophic cardiomyopathy (HCM) are thought to destabilize (decrease the population of) the IHM state. The effects of pathogenic mutations on the IHM structural state are often studied using indirect assays, including a single-ATP turnover assay that detects the super-relaxed (SRX) biochemical state of myosin functionally. Here we develop and use a fluorescence resonance energy transfer (FRET) based sensor for direct quantification of the IHM state in solution. The FRET sensor was able to quantify destabilization of the IHM state in solution, induced by (a) increasing salt concentration, (b) altering proximal S2 tail length, or (c) introducing the HCM mutation P710R, as well as stabilization of the IHM state by introducing a dilated cardiomyopathy-causing mutation (E525K). Our FRET sensor conclusively showed that these perturbations indeed alter the structural IHM state. These results establish that the structural IHM state is one of the structural correlates of the biochemical SRX state in solution.

biophysics↗

bioRxiv2024

Hypertrophic cardiomyopathy mutations Y115H and E497D disrupt the folded-back state of human beta-cardiac myosin allosterically

At the molecular level, clinical hypercontractility associated with many hypertrophic cardiomyopathy (HCM)-causing mutations in {beta}-cardiac myosin appears to be driven by their disruptive effect on the energy-conserving, folded-back, super relaxed (SRX) OFF-state of myosin. A pathological increase in force production results from release of heads from this OFF-state, which results in an increase in the number of heads free to interact with actin and produce force. Pathogenic mutations in myosin can conceivably disrupt the OFF-state by (1) directly affecting the intramolecular interfaces stabilizing the folded-back state, or (2) allosterically destabilizing the folded-back state via disruption of diverse conformational states of the myosin motor along its chemomechanical cycle. However, very little is understood about the mutations that fall in the latter group. Here, using recombinant human {beta}-cardiac myosin, we analysed the biomechanical properties of two such HCM-causing mutations, Y115H (in the transducer) and E497D (in the relay helix), neither of which falls in the regions that interact to stabilize myosins folded-back state. We find these mutations have diverse effects on the contractility parameters of myosin, yet the primary hypercontractile change in both cases is the destabilization of the OFF-state of myosin and increased availability of active myosin heads for actin-binding. Experimental data and molecular dynamics simulations indicate that these mutations likely destabilize the pre-powerstroke state of myosin, the conformation the motor adopts in the inactive folded-back state. We propose that destabilization of the folded-back state of myosin, directly and/or allosterically, is the molecular basis of hypercontractility in HCM in a far greater number of pathogenic mutations than currently thought.

biochemistry↗

bioRxiv2023

How to Scan DNA using Promiscuous Recognition and No Sliding Clamp: A Model for Pioneer Transcription Factors

DNA scanning proteins slide on the DNA assisted by a clamping interface and uniquely recognize their cognate sequence motif. The transcription factors that control cell fate in eukaryotes must forgo these elements to gain access to both naked DNA and chromatin, so whether or how they scan DNA is unknown. Here we use single-molecule techniques to investigate DNA scanning by the Engrailed homeodomain (enHD) as paradigm of promiscuous recognition and open DNA interaction. We find that enHD scans DNA as fast and extensively as conventional scanners and 10,000,000 fold faster than expected for a continuous promiscuous slide. Our results indicate that such supercharged scanning involves stochastic alternants between local sequence sweeps of [~]85 bp and very rapid deployments to locations [~]500 bp afar. The scanning mechanism of enHD reveals a strategy perfectly suited for the highly complex environments of eukaryotic cells that might be generally used by pioneer transcription factors. TeaserEukaryotic transcription factors can efficiently scan DNA using a rather special mechanism based on promiscuous recognition.

biophysics↗