title: A change of the metal-specific activity of a cambialistic superoxide dismutase from Porphyromonas gingivalis by a double mutation of Gln-70 to Gly and Ala-142 to Gln.
abstract: Gln-70, which is located near the active-site metal, is conserved in aligned amino acid sequences of iron-containing superoxide dimutases (Fe-SODs) and cambialistic SOD from Porphyromonas gingivalis, but is complementarily substituted with Gln-142 in manganese-containing SODs (Mn-SODs). In order to clarify the contribution of this exchange of Gln to the metal-specific activity of P. gingivalis SOD, we have prepared a mutant of the enzyme with conversions of Gln-70 to Gly and Ala-142 to Gln. The ratio of the specific activities of Mn- to Fe-reconstituted P. gingivalis SOD increased from 1.4 in the wild-type to 3.5 in the mutant SODs. Furthermore, the visible absorption spectra of the Mn- and Fe-reconstituted mutant SODs more closely resembled that of Mn-specific SOD than that of the wild-type SOD. We conclude that a difference in configuration of the Gln residues of P. gingivalis SOD partially accounts for the metal-specific activity of the enzyme.
authors.affiliation: Department of Oral Biochemistry, Matsumoto Dental University, Shiojiri 399-0781, Japan. yamakura@sakura.juntendo.ac.jp
authors.forename: B Y
authors.initials: BY
authors.lastname: Hiraoka
authors.forename: F
authors.initials: F
authors.lastname: Yamakura
authors.forename: S
authors.initials: S
authors.lastname: Sugio
authors.forename: K
authors.initials: K
authors.lastname: Nakayama
mesh_terms: D000409:Alanine / Q000235:genetics; D020134:Catalytic Domain; D005973:Glutamine / Q000235:genetics; D005998:Glycine / Q000235:genetics; D007501:Iron; D008345:Manganese; D008667:Metalloproteins / Q000235:genetics / Q000378:metabolism; D008956:Models, Chemical; D016297:Mutagenesis, Site-Directed; D016966:Porphyromonas gingivalis / Q000201:enzymology* / Q000235:genetics; D013053:Spectrophotometry; D013482:Superoxide Dismutase / Q000235:genetics / Q000378:metabolism*
chemical_list: D008667:Metalloproteins; D005973:Glutamine; D008345:Manganese; D007501:Iron; D013482:Superoxide Dismutase; D000409:Alanine; D005998:Glycine