Analysis of SecA dimerization in solution.
The Sec pathway mediates translocation of protein across the inner membrane of bacteria. SecA is a motor protein that drives translocation of preprotein through the SecYEG channel. SecA reversibly dimerizes under physiological conditions, but different dimer interfaces have been observed in SecA crystal structures. Here, we have used biophysical approaches to address the nature of the SecA dimer that exists in solution. We have taken advantage of the extreme salt sensitivity of SecA dimerization to compare the rates of hydrogen-deuterium exchange of the monomer and dimer and have analyzed the effects of single-alanine substitutions on dimerization affinity. Our results support the antiparallel dimer arrangement observed in one of the crystal structures of Bacillus subtilis SecA. Additional residues lying within the preprotein binding domain and the C-terminus are also protected from exchange upon dimerization, indicating linkage to a conformational transition of the preprotein binding domain from an open to a closed state. In agreement with this interpretation, normal mode analysis demonstrates that the SecA dimer interface influences the global dynamics of SecA such that dimerization stabilizes the closed conformation.
Department of Pharmaceutical Sciences, University of Connecticut , Storrs, Connecticut 06269, United States.
Andy J
AJ
Wowor
Yuetian
Y
Yan
Sarah M
SM
Auclair
Dongmei
D
Yu
Jun
J
Zhang
Eric R
ER
May
Michael L
ML
Gross
Debra A
DA
Kendall
James L
JL
Cole
D000251:Adenosine Triphosphatases / Q000737:chemistry* / Q000235:genetics; D019943:Amino Acid Substitution; D001412:Bacillus subtilis / Q000737:chemistry / Q000235:genetics; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics; D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000737:chemistry* / Q000235:genetics; D026901:Membrane Transport Proteins / Q000737:chemistry* / Q000235:genetics; D055503:Protein Multimerization / Q000502:physiology*; D020836:Protein Structure, Quaternary; D000069816:SEC Translocation Channels; D000081416:SecA Proteins
D001426:Bacterial Proteins; D026901:Membrane Transport Proteins; D000069816:SEC Translocation Channels; D000251:Adenosine Triphosphatases; D000081416:SecA Proteins