4Y7J
Structure of an archaeal mechanosensitive channel in expanded state
Summary for 4Y7J
| Entry DOI | 10.2210/pdb4y7j/pdb |
| Related | 4Y7K |
| Descriptor | Large conductance mechanosensitive channel protein,Riboflavin synthase, nonyl beta-D-glucopyranoside (2 entities in total) |
| Functional Keywords | mechanosensitive channel, mechanosensation, membrane protein, transport protein |
| Biological source | Methanosarcina acetivorans C2A More |
| Total number of polymer chains | 5 |
| Total formula weight | 154653.14 |
| Authors | |
| Primary citation | Li, J.,Guo, J.,Ou, X.,Zhang, M.,Li, Y.,Liu, Z. Mechanical coupling of the multiple structural elements of the large-conductance mechanosensitive channel during expansion Proc.Natl.Acad.Sci.USA, 112:10726-10731, 2015 Cited by PubMed Abstract: The prokaryotic mechanosensitive channel of large conductance (MscL) is a pressure-relief valve protecting the cell from lysing during acute osmotic downshock. When the membrane is stretched, MscL responds to the increase of membrane tension and opens a nonselective pore to about 30 Å wide, exhibiting a large unitary conductance of ∼ 3 nS. A fundamental step toward understanding the gating mechanism of MscL is to decipher the molecular details of the conformational changes accompanying channel opening. By applying fusion-protein strategy and controlling detergent composition, we have solved the structures of an archaeal MscL homolog from Methanosarcina acetivorans trapped in the closed and expanded intermediate states. The comparative analysis of these two new structures reveals significant conformational rearrangements in the different domains of MscL. The large changes observed in the tilt angles of the two transmembrane helices (TM1 and TM2) fit well with the helix-pivoting model derived from the earlier geometric analyses based on the previous structures. Meanwhile, the periplasmic loop region transforms from a folded structure, containing an ω-shaped loop and a short β-hairpin, to an extended and partly disordered conformation during channel expansion. Moreover, a significant rotating and sliding of the N-terminal helix (N-helix) is coupled to the tilting movements of TM1 and TM2. The dynamic relationships between the N-helix and TM1/TM2 suggest that the N-helix serves as a membrane-anchored stopper that limits the tilts of TM1 and TM2 in the gating process. These results provide direct mechanistic insights into the highly coordinated movement of the different domains of the MscL channel when it expands. PubMed: 26261325DOI: 10.1073/pnas.1503202112 PDB entries with the same primary citation |
| Experimental method | X-RAY DIFFRACTION (4.1 Å) |
Structure validation
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