title: In vitro and in vivo oxidation of methionine residues in small, acid-soluble spore proteins from Bacillus species.
abstract: Methionine residues in alpha/beta-type small, acid-soluble spore proteins (SASP) of Bacillus species were readily oxidized to methionine sulfoxide in vitro by t-butyl hydroperoxide (tBHP) or hydrogen peroxide (H2O2). These oxidized alpha/beta-type SASP no longer bound to DNA effectively, but DNA binding protected alpha/beta-type SASP against methionine oxidation by peroxides in vitro. Incubation of an oxidized alpha/beta-type SASP with peptidyl methionine sulfoxide reductase (MsrA), which can reduce methionine sulfoxide residues back to methionine, restored the alpha/beta-type SASP's ability to bind to DNA. Both tBHP and H2O2 caused some oxidation of the two methionine residues of an alpha/beta-type SASP (SspC) in spores of Bacillus subtilis, although one methionine which is highly conserved in alpha/beta-type SASP was only oxidized to a small degree. However, much more methionine sulfoxide was generated by peroxide treatment of spores carrying a mutant form of SspC which has a lower affinity for DNA. MsrA activity was present in wild-type B. subtilis spores. However, msrA mutant spores were no more sensitive to H2O2 than were wild-type spores. The major mechanism operating for dealing with oxidative damage to alpha/beta-type SASP in spores is DNA binding, which protects the protein's methionine residues from oxidation both in vitro and in vivo. This may be important in vivo since alpha/beta-type SASP containing oxidized methionine residues no longer bind DNA well and alpha/beta-type SASP-DNA binding is essential for long-term spore survival.
authors.affiliation: Department of Biochemistry, University of Connecticut Health Center, Farmington, Connecticut 06030, USA.
authors.forename: C S
authors.initials: CS
authors.lastname: Hayes
authors.forename: B
authors.initials: B
authors.lastname: Illades-Aguiar
authors.forename: L
authors.initials: L
authors.lastname: Casillas-Martinez
authors.forename: P
authors.initials: P
authors.lastname: Setlow
mesh_terms: D001407:Bacillus / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism*; D008715:Methionine / Q000378:metabolism*; D010084:Oxidation-Reduction; D013171:Spores, Bacterial / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D008715:Methionine