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Dynamics of the general secretory system viewed in near‐native conditions via atomic force microscopy (993.1)
Author(s) -
King Gavin,
Sanganna Gari Raghavendar Reddy,
Frey Nathan,
Mao Chungfeng,
Randall Linda
Publication year - 2014
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.28.1_supplement.993.1
Subject(s) - translocase , biophysics , cytoplasm , transmembrane protein , secretory protein , lipid bilayer , atomic force microscopy , chemistry , population , membrane , biology , nanotechnology , biochemistry , secretion , materials science , chromosomal translocation , receptor , demography , sociology , gene
In bacteria and archaea the protein conducting channel SecYEG provides a ubiquitous pathway for protein transfer across and into membranes. Further, it is known that SecA is the ATPase of the general secretory system and it binds SecYEG to perform translocation. In so doing, SecA makes large surface area contact with the unstructured cytoplasmic loops spanning transmembrane helices 6‐7 and 8‐9 of SecY. Despite their functional significance, measurements of flexible and disordered protein domains remain a significant experimental challenge. Recently, atomic force microscopy (AFM) has emerged as an important complementary tool in biophysics and is well suited for studying membrane protein dynamics in near‐native conditions (i.e., in a native lipid environment, at physiologically relevant temperature and ionic strength). We have studied purified SecYEG that was reconstituted into liposomes via AFM. After confirming activity, changes in the structure of SecYEG as a function of time were directly visualized. The dynamics observed were significant in magnitude and were attributed to the aforementioned loops of SecY. In addition, we identified a distribution between monomers and dimers of SecYEG as well as a smaller population of higher order oligomers. Finally, we have imaged SecA engaged on SecYEG and related the structural states observed to the activity of the translocase. This work provides a novel and near‐native vista of central components of the general secretory system. Grant Funding Source : This work was supported by the National Science Foundation CAREER Award 1054832 (to G. M. K.)