title: Mycoplasma gallisepticum produces a histone-like protein that recognizes base mismatches in DNA.
abstract: Mycoplasmas are the smallest known microorganisms, with drastically reduced genome sizes. One of the essential biochemical pathways lost in mycoplasmas is methylation-mediated DNA repair (MMR), which is responsible for correction of base substitutions, insertions, and deletions in both bacteria and higher organisms. We found that the histone-like protein encoded by the himA/hup_2 gene of Mycoplasma gallisepticum (mgHU) recognizes typical MMR substrates, in contrast to homologues from other species. The recognition of substitution mismatches is sequence-dependent, with affinities decreasing in the following order: CC > CT = TT > AA = AC. Insertions or deletions of one nucleotide are also specifically recognized with the following sequence-dependent preference: A = T > C. One-nucleotide lesions involving guanine are bound only weakly, and this binding is indistinguishable from binding to intact DNA. Although mgHU is dissimilar to Escherichia coli HU, expression in a slow-growing hupAB E. coli strain restores wild-type growth. The results indicate that mgHU executes all essential functions of bacterial architectural proteins. The origin and the possible role of enhanced specificity for typical MMR substrates are discussed.
authors: Research Institute for Physico-Chemical Medicine, Moscow 119435, Russia. dkamashev@gmail.com
authors: Dmitri
authors: D
authors: Kamashev
authors: Jacques
authors: J
authors: Oberto
authors: Marina
authors: M
authors: Serebryakova
authors: Alexey
authors: A
authors: Gorbachev
authors: Yulia
authors: Y
authors: Zhukova
authors: Sergei
authors: S
authors: Levitskii
authors: Alexey K
authors: AK
authors: Mazur
authors: Vadim
authors: V
authors: Govorun
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D020137:Base Pair Mismatch; D001483:Base Sequence; D053843:DNA Mismatch Repair; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D045686:Mycoplasma gallisepticum / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D016415:Sequence Alignment; D013379:Substrate Specificity
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C040330:histone-like protein HU, bacteria; C116822:hns protein, E coli