Primary sequence analysis of Clostridium cellulovorans cellulose binding protein A

The cbpA gene for the Clostridium cellulovorans cellulose binding protein (CbpA), which is part of the multisubunit cellulase complex, has been cloned and se-quenced. When cbpA was expressed in Escherichia coli, proteins capable of binding to crystalline cellulose and of interacting with anti-CbpA were observed. The cbpA gene consists of 5544 base pairs and encodes a protein containing 1848 amino acids with a molecular mass of 189,036 Da. The open reading frame is preceded by a Gram-positive-type ribosome binding site. A signal peptide sequence of 28 amino acids is present at its N terminus. The encoded protein is highly hydrophobi with extremely high levels of threonine and valine residues. There are two types of putative cellulose binding domains of ≈100 amino acids that are slightly hydrophilic and eight conserved, highly hydropbobic β-sheet regions of ≈140 amino acids. These letter hydrophobic regions may be the CbpA domains that interact with the different enzymatic subunits of the cellulase complex.