Functional Cycle of a Mechanosensitive Channel

机械敏感通道的功能周期

• 批准号: 7370990
• 负责人: SERGEI I SUKHAREV
• 金额: $ 27.4万
• 依托单位: UNIV OF MARYLAND, COLLEGE PARK
• 依托单位国家: 美国
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-03-01 至 2010-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7370990
• 关键词: Accounting; Affect; Bacteria; Biological Assay; Biological Models; Biophysics; Caliber; Cell membrane; Charge; Cholinergic Receptors; Constriction procedure; Cysteine; Data; Data Analyses; Disulfides; Engineering; Equilibrium; Eukaryota; Eukaryotic Cell; Event; Family; Foundations; Helix (Snails); Homologous Gene; Hydration status; Kinetics; Life; Link; Lipid Bilayers; Lipids; Location; Measurement; Mechanics; Membrane; Modeling; Modification; Molecular; Molecular Conformation; Movement; Mutagenesis; Mutation; Play; Process; Prokaryotic Cells; Property; Proteins; Reagent; Regulation; Research; Rest; Role; Sensory; Series; Shapes; Simulate; Solutions; Staging; Stretching; Structure; Study models; System; Testing; Water; Work; aqueous; base; crosslink; desire; ear helix; gain of function; interest; models and simulation; molecular dynamics; mutant; novel; patch clamp; periplasm; pressure; research study; simulation; vapor; voltage

The small mechanosensitive channel MscS, a ubiquitous bacterial osmoregulator, is an advanced model system for biophysical studies of the initial events in mechanotransduction. The solved crystal structure and the existence of eukaryotic homologs make MscS especially attractive. Our preliminary data, both experimental and computational, lay the foundation for a new hypothesis about the gating mechanism of MscS which we now present as a series of conformational states and transitions derived from the crystal structure. Despite previous notions that MscS is a tension and voltage-activated channel, we found its activation by tension rather voltage-independent. However, the process of inactivation was strongly promoted by depolarization. Computational assessment of the crystal structure suggested that the pore is dehydrated and its conformation represents a non-conducting, likely inactivated state. Using targeted energy minimizations we have envisioned a gating cycle which begins with a compact resting conformation of the barrel with transmembrane helices tightly packed around the pore. Opening is achieved through a concerted outward movement of helices associated with wetting and expansion of the pore constriction. Inactivation occurs when the pore-forming TM3 helices decouple from the lipid-facing TM1 and TM2 helices and collapse into a narrow (crystal-like) conformation. To test this hypothesis we will (1) perform steered molecular dynamics simulations and generate accurate models for the closed and open states; (2) verify the predicted proximities of critical residues by disulfide cross-linking and test the functional consequences of bridge formation in patch-clamp experiments; (3) test accessibilities of residues in the pore and crevices using cysteine substitutions and MTS reagents; (4) evaluate the contribution of the pore hydration to the gating energetics and validate the previously proposed Vapor lock' mechanism. The work, when accomplished, will move us closer toward understanding the mechanisms of the growing families of sensory channels.

小的机械敏感通道MscS是一种普遍存在的细菌渗透调节剂，是一种先进的模型