title: Evidence of met-form myoglobin from Theliostyla albicilla radular muscle.
abstract: Gastropod mollusc myoglobins provide interesting clues to the evolution of this family of proteins. In addition to conventional monomeric myoglobins, this group also has dimeric and unusual indoleamine dioxygenase-like myoglobins. We isolated myoglobin from the radular muscle of living gastropod mollusc Theliostyla albicilla. The myoglobin appeared to be present in an oxidized met-form, a physiologically inactive form that is not capable of binding oxygen. Under the same extraction conditions, myoglobins mainly of the physiologically active oxy-form have been isolated from other molluscs. The complete amino acid sequence of 157 residues of Theliostyla myoglobin shows that it has a long N-terminal extension of seven residues and contains three functional key residues: CD1-Phe, E7-His, and F8-His. The metmyoglobin can easily be reduced to a ferrous state with Na(2)S(2)O(4). The autoxidation rate of the oxy-form was comparable to other molluscan myoglobins over a wide pH range, and Theliostyla myoglobin was shown to be stable as an oxygen-binding protein. Thus, the predominantly met-form of myoglobin in Theliostyla can be attributed to the incomplete functioning of the myoglobin reduction system in the radular muscle. Although the function of Theliostyla myoglobin is unclear, it may be a scavenger of H(2)O(2).
authors.affiliation: Laboratory of Biochemistry, Faculty of Science, Kochi University, Kochi 780-8520, Japan. suzuki@cc.kochi-u.ac.jp
authors.forename: Tomohiko
authors.initials: T
authors.lastname: Suzuki
authors.forename: Hideaki
authors.initials: H
authors.lastname: Takao
authors.forename: Kazuko
authors.initials: K
authors.lastname: Yamanaka
authors.forename: Harumi
authors.initials: H
authors.lastname: Gotoh
authors.forename: Takahiro
authors.initials: T
authors.lastname: Furukohri
authors.forename: Takashi
authors.initials: T
authors.lastname: Takagi
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002850:Chromatography, Gel; D006863:Hydrogen-Ion Concentration; D008786:Metmyoglobin / Q000378:metabolism*; D008969:Molecular Sequence Data; D008974:Mollusca / Q000378:metabolism*; D009132:Muscles / Q000737:chemistry / Q000378:metabolism*; D009211:Myoglobin / Q000378:metabolism; D010084:Oxidation-Reduction; D010802:Phylogeny; D017385:Sequence Homology
chemical_list: D009211:Myoglobin; C017595:oxymyoglobin; D008786:Metmyoglobin