Pressure sensing at a molecular level James H Naismith The - - PowerPoint PPT Presentation

Pressure sensing at a molecular level

James H Naismith The University, St Andrews (est 1411)

Acknowledgements

• Wenjiang Wang, Changjiang Dong, Kostas Beis,

Gregor Hageluken, Emma Brannigan, Christos Pliotas*, Richard Ward, Phedra Marius, Terry Smith, Jim Naismith & Olav Schiemann

• Ian Booth, Michelle Edwards, Susan Black, Sam

Miller, Wendy Bartlett, Akikio Rasmussen (Aberdeen)

• Hagan Bayley, Mahendran (Oxford)
• Friendly discussion Bass & Rees; Perozo

BBSRC, Wellcome Trust, St Andrews

Mechanosensitive channels

• Bacteria experience rapid changes in osmotic

pressure

• Without the release of ions from inside

cytoplasm, they would explode

– Transfer to water creates pressures of > 14 atm

• Mechanosensitive channels open, allowing rapid

efflux of ions and small solutes

• Need tight seal normally
• Relatively small free energy between states

A priori

• Structures came from the Rees lab :

– MscL 3.5 Å structure (G. Chang, et al, Science 282, 2220 (1998)) new structure Liu et al., 2009, Nature, 461, 120-4) – MscS 3.95 Å, (R. Bass et al, Science 298, 1582 (2002)

• Open to close transitions

– Model: Sukharev et al., Nature 409, 720 (2000) – EPR: Perozo, Nature 418, 942 (2002) – FRET: Corry, Biophys 91, 1032 (2006); Martinac, B.,

• Lipids

– Blount, P.; Perozo, E. and Lee, A.

Mechanosensitive channels

Taken from Naismith & Booth, 2012

How does MscS feel pressure?

Lyso-PC simulates pressure

Closed book?

NATURE STRUCTURAL & MOLECULAR BIOLOGY VOLUME 14, 1141

Compact barrel with C Cytoplasm N Periplasm

a d e

3.1 Å D67R1 structure

A& B& C&

PE lipids are bound to MscS

6 6 5 7 7 5 8 8 5 9 9 5 1 m /z, D a .0 2 .0 e 8 4 .0 e 8 6 .0 e 8 8 .0 e 8 1 .0 e 9 1 .2 e 9 1 .4 e 9 1 .6 e 9 In ten sity, cp s

7 3 4 .1 6 7 2 .1 6 7 4 8 .1 6 7 6 2 .2 4 7 2 2 .1 6 7 7 4 .1 6 7 3 6 .1 6 7 4 6 .1 6 6 9 4 .2 4 7 7 5 .1 2 7 8 .2 4 7 5 .1 6 7 6 4 .0 8 6 9 2 .1 6 6 6 6 .1 6 8 2 .1 6 7 1 8 .2 4 8 4 6 .3 2 9 4 2 .3 2 9 1 6 .3 2 9 9 2 .3 2 8 8 8 .2 4 6 3 8 .3 2 8 2 4 .0 8 8 5 3 .8 4

PG 30:1 PG 34:1 PG 32:1 PG 36:2 PG 33:1 PG 28:0 PE 35:1 PG 31:0

6 6 5 7 7 5 8 8 5 9 9 5 1 m /z, D a .0 5 .0 e 6 1 .0 e 7 1 .5 e 7 2 .0 e 7 2 .5 e 7 3 .0 e 7 3 .2 e 7 In ten sity, cp s

7 2 .4 7 4 8 .5 6 6 9 2 .3 2 6 5 6 .4 6 9 4 .3 2 7 4 6 .4 8 6 .8 8 7 7 4 .5 6 6 8 2 .3 2 7 2 2 .0 8 7 3 4 .1 6 6 2 .0 7 1 8 .4 7 6 6 .4 8 6 8 9 .2 8 7 7 6 .0 6 7 .4 6 4 2 .4 6 3 .9 2 6 8 4 .0 8 7 2 3 .6 8 8 1 2 .7 2 7 7 .4 08 4 .0 7 2 9 .6 9 5 3 .3 6 6 9 1 .0 4 8 5 8 .0 8 8 8 .0 6 2 8 .4 9 6 8 .7 2 8 2 4 .3 2 6 6 1 .7 6 8 9 7 .2 8 9 1 6 .8 8 7 8 4 .2 4 7 5 .5 2 7 5 8 .4 8 6 2 2 .0 8 9 7 .4 8 7 7 .7 6 9 9 5 .6 8

PE 30:2 PE 32:3 PE 26:0 PG 30:1 PG 34:1 PG 32:1 PG 36:2 Extracted Figure&X2.&Lipidomics&analysis&of&purified&MscS&D67R1&and&expression&background&strain&

PE PG

Molecular model of pressure sensing

reased$turgor$pressure,$membrane$stretches,$$ lipids$move$to$bilayer$ Open$conformaUon$

• Our model based on differential lipidation; different but

related to Schmidt & Mackinnon PNAS 2013. Looking again at Kv, shows it too has very different lipid interacting regions in the open from the closed structure