Matano Y, Park J S, Goldstein M A, Doi R H
Section of Molecular and Cellular Biology, University of California, Davis 95616.
J Bacteriol. 1994 Nov;176(22):6952-6. doi: 10.1128/jb.176.22.6952-6956.1994.
Cellulosome synthesis by Clostridium cellulovorans was investigated by growing the cells in media containing different carbon sources. Supernatant from cells grown with cellobiose contained no cellulosomes and only the free forms of cellulosomal major subunits CbpA, P100, and P70 and the minor subunits with enzymatic activity. Supernatant from cells grown on pebble-milled cellulose and Avicel contained cellulosomes capable of degrading crystalline cellulose. Supernatants from cells grown with cellobiose, pebble-milled cellulose, and Avicel contained about the same amount of carboxymethyl cellulase activity. Although the supernatant from the medium containing cellobiose did not initially contain active cellulosomes, the addition of crystalline cellulose to the cell-free supernatant fraction converted the free major forms to cellulosomes with the ability to degrade crystalline cellulose. The binding of P100 and P70 to crystalline cellulose was dependent on their attachment to the endoglucanase-binding domains of CbpA. These data strongly indicate that crystalline cellulose promotes cellulosome assembly.
通过在含有不同碳源的培养基中培养细胞，研究了食纤维梭菌（Clostridium cellulovorans）的纤维小体合成。以纤维二糖培养的细胞的上清液中不含纤维小体，仅含有纤维小体主要亚基CbpA、P100和P70的游离形式以及具有酶活性的次要亚基。以经卵石研磨的纤维素和微晶纤维素培养的细胞的上清液中含有能够降解结晶纤维素的纤维小体。以纤维二糖、经卵石研磨的纤维素和微晶纤维素培养的细胞的上清液中羧甲基纤维素酶活性大致相同。虽然含有纤维二糖的培养基的上清液最初不含活性纤维小体，但向无细胞上清液组分中添加结晶纤维素可将游离的主要形式转化为具有降解结晶纤维素能力的纤维小体。P100和P70与结晶纤维素的结合取决于它们与CbpA的内切葡聚糖酶结合结构域的附着。这些数据有力地表明结晶纤维素促进纤维小体组装。
