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The mechanism of protein export enhancement by the SecDF membrane component

View Article: PubMed Central - PubMed

ABSTRACT

Protein transport across membranes is a fundamental and essential cellular activity in all organisms. In bacteria, protein export across the cytoplasmic membrane, driven by dynamic interplays between the protein-conducting SecYEG channel (Sec translocon) and the SecA ATPase, is enhanced by the proton motive force (PMF) and a membrane-integrated Sec component, SecDF. However, the structure and function of SecDF have remained unclear. We solved the first crystal structure of SecDF, consisting of a pseudo-symmetrical 12-helix transmembrane domain and two protruding periplasmic domains. Based on the structural features, we proposed that SecDF functions as a membrane-integrated chaperone, which drives protein movement without using the major energetic currency, ATP, but with remarkable cycles of conformational changes, powered by the proton gradient across the membrane. By a series of biochemical and biophysical approaches, several functionally important residues in the transmembrane region have been identified and our model of the SecDF function has been verified.

No MeSH data available.


Conformational transition of SecDF. Stereo-views of the F form (a) and the I form (b).
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f3-7_129: Conformational transition of SecDF. Stereo-views of the F form (a) and the I form (b).

Mentions: A comparison of the full-length crystal structure (called the F form; Fig. 3a) with the model of the SecDF structure, which was built by superimposing the base subdomain of the isolated P1 structure (PDB ID 3AQO) onto that of the full-length SecDF (called the I form; Fig. 3b), revealed a significant difference in the head-to-base orientation of the P1 domain. This conformational change is due to the ~120° rigid-body rotation of the head domain, which is attributed to a hinge motion at the connecting loops between the head and base domains.


The mechanism of protein export enhancement by the SecDF membrane component
Conformational transition of SecDF. Stereo-views of the F form (a) and the I form (b).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC5036778&req=5

f3-7_129: Conformational transition of SecDF. Stereo-views of the F form (a) and the I form (b).
Mentions: A comparison of the full-length crystal structure (called the F form; Fig. 3a) with the model of the SecDF structure, which was built by superimposing the base subdomain of the isolated P1 structure (PDB ID 3AQO) onto that of the full-length SecDF (called the I form; Fig. 3b), revealed a significant difference in the head-to-base orientation of the P1 domain. This conformational change is due to the ~120° rigid-body rotation of the head domain, which is attributed to a hinge motion at the connecting loops between the head and base domains.

View Article: PubMed Central - PubMed

ABSTRACT

Protein transport across membranes is a fundamental and essential cellular activity in all organisms. In bacteria, protein export across the cytoplasmic membrane, driven by dynamic interplays between the protein-conducting SecYEG channel (Sec translocon) and the SecA ATPase, is enhanced by the proton motive force (PMF) and a membrane-integrated Sec component, SecDF. However, the structure and function of SecDF have remained unclear. We solved the first crystal structure of SecDF, consisting of a pseudo-symmetrical 12-helix transmembrane domain and two protruding periplasmic domains. Based on the structural features, we proposed that SecDF functions as a membrane-integrated chaperone, which drives protein movement without using the major energetic currency, ATP, but with remarkable cycles of conformational changes, powered by the proton gradient across the membrane. By a series of biochemical and biophysical approaches, several functionally important residues in the transmembrane region have been identified and our model of the SecDF function has been verified.

No MeSH data available.