HDX-MS reveals nucleotide-dependent, anti-correlated opening and closure of SecA and SecY channels of the bacterial translocon

TY - JOUR

T1 - HDX-MS reveals nucleotide-dependent, anti-correlated opening and closure of SecA and SecY channels of the bacterial translocon

AU - Ahdash, Zainab

AU - Pyle, Euan

AU - Allen, William John

AU - Corey, Robin A

AU - Collinson, Ian

AU - Politis, Argyris

N1 - © 2019, Ahdash et al.

PY - 2019/7/10

Y1 - 2019/7/10

N2 - The bacterial Sec translocon is a multi-protein complex responsible for translocating diverse proteins across the plasma membrane. For post-translational protein translocation, the Sec-channel - SecYEG - associates with the motor protein SecA to mediate the ATP-dependent transport of pre-proteins across the membrane. Previously, a diffusional-based Brownian ratchet mechanism for protein secretion has been proposed; the structural dynamics required to facilitate this mechanism remain unknown. Here, we employ hydrogen-deuterium exchange mass spectrometry (HDX-MS) to reveal striking nucleotide-dependent conformational changes in the Sec protein-channel from Escherichia coli. In addition to the ATP-dependent opening of SecY, reported previously, we observe a counteracting, and ATP-dependent, constriction of SecA around the pre-protein. ATP binding causes SecY to open and SecA to close; while, ADP produced by hydrolysis, has the opposite effect. This alternating behaviour could help impose the directionality of the Brownian ratchet for protein transport through the Sec machinery.

AB - The bacterial Sec translocon is a multi-protein complex responsible for translocating diverse proteins across the plasma membrane. For post-translational protein translocation, the Sec-channel - SecYEG - associates with the motor protein SecA to mediate the ATP-dependent transport of pre-proteins across the membrane. Previously, a diffusional-based Brownian ratchet mechanism for protein secretion has been proposed; the structural dynamics required to facilitate this mechanism remain unknown. Here, we employ hydrogen-deuterium exchange mass spectrometry (HDX-MS) to reveal striking nucleotide-dependent conformational changes in the Sec protein-channel from Escherichia coli. In addition to the ATP-dependent opening of SecY, reported previously, we observe a counteracting, and ATP-dependent, constriction of SecA around the pre-protein. ATP binding causes SecY to open and SecA to close; while, ADP produced by hydrolysis, has the opposite effect. This alternating behaviour could help impose the directionality of the Brownian ratchet for protein transport through the Sec machinery.

KW - E. coli

KW - SecA

KW - SecYEG

KW - conformational dynamics

KW - hydrogen-deuterium exchange mass spectromtery

KW - molecular biophysics

KW - protein translocation

KW - structural biology

UR - http://www.scopus.com/inward/record.url?scp=85070055882&partnerID=8YFLogxK

U2 - 10.7554/eLife.47402

DO - 10.7554/eLife.47402

M3 - Article

C2 - 31290743

SN - 2050-084X

VL - 8

JO - eLife

JF - eLife

M1 - e47402

ER -