title: Copper (II) ions affect Escherichia coli membrane vesicles' SH-groups and a disulfide-dithiol interchange between membrane proteins.
abstract: The SH-groups in Escherichia coli membrane vesicles, prepared from cells grown in fermentation conditions on glucose at slightly alkaline pH, have a role in the F0F1-ATPase operation. The changes in the number of these groups by ATP are observed under certain conditions. In this study, copper ions (Cu2+) in concentration of 0.1 mM were shown to increase the number of SH-groups in 1.5- to 1.6-fold independent from K+ ions, and the suppression of the increased level of SH-groups by ATP was determined for Cu2+ in the presence of K+. Moreover, the increase in the number of SH-groups by Cu2+ was absent as well as the inhibition in ATP-dependent increasing SH-groups number by Cu2+ lacked when vesicles were treated with N-ethylmaleimide (NEM), specific thiol-reagent. Such an effect was not observed with zinc (Zn2+), cobalt (Co2+), or Cu+ ions. The increased level of SH-groups was observed in the hycE or hyfR mutants with defects in hydrogenases 3 or 4, whereas the ATP-dependent increase in the number of these groups was determined in hycE not in hyfR mutants. Both changes in SH-groups number disappeared in the atp or hyc mutants deleted for the F0F1-ATPase or hydrogenase 3 (no activity of hydrogenase 4 was detected in the hyc mutant used). A direct effect of Cu2+ but not Cu+ on the F0F1-ATPase is suggested to lead to conformational changes or damaging consequences, increasing accessible SH-groups number and disturbing disulfide-dithiol interchange within a protein-protein complex, where this ATPase works with K+ uptake system or hydrogenase 4 (Hyd-4); breaks in disulfides are not ruled out.
authors.affiliation: Department of Biophysics of the Biological Faculty, Yerevan State University, 1 Alex Manougian Str, Yerevan 0025, Armenia.
authors.forename: Gayane
authors.initials: G
authors.lastname: Kirakosyan
authors.forename: Karen
authors.initials: K
authors.lastname: Trchounian
authors.forename: Zaruhi
authors.initials: Z
authors.lastname: Vardanyan
authors.forename: Armen
authors.initials: A
authors.lastname: Trchounian
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D002462:Cell Membrane / Q000737:chemistry / Q000187:drug effects* / Q000378:metabolism; D003035:Cobalt / Q000494:pharmacology; D003300:Copper / Q000494:pharmacology*; D003545:Cysteine; D004220:Disulfides / Q000378:metabolism*; D004926:Escherichia coli / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D005285:Fermentation; D006864:Hydrogenase / Q000235:genetics / Q000378:metabolism; D008565:Membrane Proteins / Q000737:chemistry* / Q000378:metabolism*; D009154:Mutation; D013438:Sulfhydryl Compounds / Q000378:metabolism*; D015032:Zinc / Q000494:pharmacology
chemical_list: D001426:Bacterial Proteins; D004220:Disulfides; D008565:Membrane Proteins; D013438:Sulfhydryl Compounds; D003035:Cobalt; D003300:Copper; D000255:Adenosine Triphosphate; D006864:Hydrogenase; D000251:Adenosine Triphosphatases; D015032:Zinc; D003545:Cysteine