CELLULOSE-BINDING PROTEINS OF FIBROBACTER-SUCCINOGENES AND THE POSSIBLE ROLE OF A 180-KDA CELLULOSE-BINDING GLYCOPROTEIN IN ADHESION TO CELLULOSE

Fibiobacter succinogenes possesses seven cellulose-binding proteins (C BPs) of 40, 45, 50, 120, 180, 220, and 240 kDa. The 120-, 180-, 220-, and 240-kDa proteins were present in the outer membrane (OM), while th e 40-, 45-, 50-, and 120-kDa proteins were either periplasmic or perip heral membrane proteins. The 120-kDa CBP, which was identified as endo glucanase 2, was a major component in both the OM and periplasm. Zymog ram analysis for glucanases showed that the major membrane-associated CBPs, with the exception of endoglucanase 2, lacked endoglucanase acti vity. Affinity purified antibodies against the 180-kDa CBP cross-react ed strongly with numerous cell envelope proteins of higher and lower m olecular mass, including the previously characterized chloride-stimula ted cellobiosidase. Treatment of the 180-kDa CBP and cell envelope pro teins with periodate resulted in almost complete loss of antibody bind ing, suggesting that they possessed a common epitope that was carbohyd rate in nature. Immunogold labelling of whole cells using antibodies a gainst the 180-kDa CBP demonstrated that either the 180-kDa CBP or rel ated proteins with a cross-reactive epitope were located at the cell s urface. These epitopes were distributed uniformly on cells not bound t o cellulose but congregated on the cell surface at sites of adhesion o f cells to cellulose. Antibodies to the 180-kDa protein caused 62% inh ibition of binding of F. succinogenes to crystalline cellulose, which provides evidence that either the 180-kDa CBP and (or) other related c ross-reactive surface proteins have a role in adhesion to cellulose.