Function of cell-adhesion protein MFBA in fruiting-body formation of basidiomycete

点击翻译按钮获取中文摘要

Fruiting of basidiomycetes is one of the most typical morphogenetic phenomena observed in eukaryotic microorganisms. We so far isolated new gene mfbA which is adjacent to ras gene and expressed strongly in mature fruiting bodies. mfbA is also expressed in immature fruiting bodies. The mfbA cDNA cloned consisted of 6700 bp encoding 2157 amino acids. MFBA protein (MW234,494) contained the cell surface attachment-promoting amino acid sequence Arg-Gly-Asp (RGD) observed first in fibronectin.This research aimed to assess the function of MFBA.Although we failed in producing intact MFBA protein, a 425-amino-acid MFBA fragment containing the RGD motif (named MFBA (582-1006) peptide) was successfully producted in E.coli. By using this MFBA fragment, the following new experimental results were obtained.(1) MFBA (582-1006) peptide exhibits a cell adhesion and spreading activity toward mammalian cells via the RGD sequence.(2) The peptide causes significant in vivo aggrefation of the yeast S.cerevisiae cells via the RGD sequence.(3) The peptide causes significant in vitro aggregation of basidiomycetous hyphal cells via RGD sequence.(4) The mfbA transcript is abundant in the gill-depleted pileus and stipe, but almost no transcript is found in the gill tissue.(5) MFBA (582-1006) peptide possesses a highly hydrophobic region adjacent to the RGD motif.These results strongly suggest that the hydrophobic region of MFBA is embedded in basidiomycetous hyphal cell wall and the RGD-containing amino acid sequence interacts with the receptor protein molecules being present on the surface of other cells via the RGD sequence. These protein-protein interactions results in formation of the net structure of basidiomycetous hyphal cells. MFBA is considered to be involved in maturation of fruiting body and formation of pileus and stipe of fruiting body.