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Biochemical characterization, intracellular localization, and stage‐specific expression of a new type of membrane‐bound β‐glucosidase from Physarum polycephalum
Author(s) -
Hayase Masato,
Yubisui Toshitsugu,
Minami Yoshiko
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.1219.3
Subject(s) - physarum polycephalum , biochemistry , molecular mass , physarum , extracellular , enzyme , transmembrane protein , intracellular , transmembrane domain , biology , peptide sequence , ribonuclease , amino acid , chemistry , rna , receptor , gene
Physarum polycephalum , one of the true slime molds, has a unique life cycle including the diploid plasmodium. The plasmodia express three forms of β‐glucosidase: an intracellular soluble, membrane‐bound, and extracellular enzyme. Specially, we focus on the membrane‐bound β‐glucosidase, BglM1, of which molecluar mass is 130 kDa. Glycosyl hydrolase familly 3 domain is found within the N‐terminal half of BglM1. Notably, the C‐terminal half of BglM1 contains two calx‐β motifs known as calcium binding sites, an RGD sequence, and a transmembrane region. Thus, Physarum BglM1 is a new type of β‐glucosidase that differs from all previously identified family 3 enzymes. The expression of BglM1 was found only in the plasmodia and microplasmodia during life cycle. The observation by immunofluorescence microscopy indicated that BglM1 is located on the cell membrane. The molecular mass of native BglM1 in microplasmodia was estimated to be 230kDa instead of 130kDa calculated from the amino acid sequence. During BglM1 was purified, its apparent size decreased from 230 to 130kDa gradually. However, when BglM1 was purified in the presence of calcium ion, the molecular mass of enzymes was held on 230kDa. These results suggest that calcium ion influences the conformation of BglM1. Based on these results, we will discuss on the function of BglM1.