Cloning and DNA Sequencing of the Genes Encoding <i>Clostridium josui</i> Scaffolding Protein CipA and Cellulase CelD and Identification of Their Gene Products as Major Components of the Cellulosome

Abstract

The Clostridium josui cipA and celD genes, encoding a scaffolding-like protein (CipA) and a putative cellulase (CelD), respectively, have been cloned and sequenced. CipA, with an estimated molecular weight of 120,227, consists of an N-terminal signal peptide, a cellulose-binding domain of family III, and six successive cohesin domains. The molecular architecture of C. josui CipA is similar to those of the scaffolding proteins reported so far, such as Clostridium thermocellum CipA, Clostridium cellulovorans CbpA, and Clostridium cellulolyticum CipC, but C. josui CipA is considerably smaller than the other scaffolding proteins. CelD consists of an N-terminal signal peptide, a family 48 catalytic domain of glycosyl hydrolase, and a dockerin domain. N-terminal amino acid sequence analysis of the C. josui cellulosomal proteins indicates that both CipA and CelD are major components of the cellulosome.