title: The variable subdomain of Escherichia coli SecA functions to regulate SecA ATPase activity and ADP release.
abstract: Bacterial SecA proteins can be categorized by the presence or absence of a variable subdomain (VAR) located within nucleotide-binding domain II of the SecA DEAD motor. Here we show that VAR is dispensable for SecA function, since the VAR deletion mutant secAΔ519-547 displayed a wild-type rate of cellular growth and protein export. Loss or gain of VAR is extremely rare in the history of bacterial evolution, indicating that it appears to contribute to secA function within the relevant species in their natural environments. VAR removal also results in additional secA phenotypes: azide resistance (Azi(r)) and suppression of signal sequence defects (PrlD). The SecAΔ(519-547) protein was found to be modestly hyperactive for SecA ATPase activities and displayed an accelerated rate of ADP release, consistent with the biochemical basis of azide resistance. Based on our findings, we discuss models whereby VAR allosterically regulates SecA DEAD motor function at SecYEG.
authors.affiliation: Department of Molecular Biology and Biochemistry, Wesleyan University, Middletown, Connecticut, USA.
authors.forename: Sanchaita
authors.initials: S
authors.lastname: Das
authors.forename: Lorry M
authors.initials: LM
authors.lastname: Grady
authors.forename: Jennifer
authors.initials: J
authors.lastname: Michtavy
authors.forename: Yayan
authors.initials: Y
authors.lastname: Zhou
authors.forename: Frederick M
authors.initials: FM
authors.lastname: Cohan
authors.forename: Manju M
authors.initials: MM
authors.lastname: Hingorani
authors.forename: Donald B
authors.initials: DB
authors.lastname: Oliver
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism*; D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D053487:DEAD-box RNA Helicases / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology*; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology*; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D010802:Phylogeny; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D000069816:SEC Translocation Channels; D000081416:SecA Proteins
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; D000069816:SEC Translocation Channels; D000244:Adenosine Diphosphate; D000251:Adenosine Triphosphatases; C088840:deaD protein, E coli; D053487:DEAD-box RNA Helicases; D000081416:SecA Proteins