THE CELL WALL-ANCHORED STREPTOMYCES-RETICULI AVICEL-BINDING PROTEIN (ABPS) AND ITS GENE

Streptomyces reticuli produces a 35-kDa cellulase-binding protein (Abp S) which interacts strongly with crystalline forms of cellulose (Avice l, bacterial microcrystalline cellulose, and tunicin cellulose); other polysaccharides are recognized on weakly (chitin and Valonia cellulos e) or not at all (xylan, starch, and agar). The protein could be purif ied to homogeneity due to its affinity to Avicel. After we sequenced i nternal peptides, the corresponding gene was identified by reverse gen etics. In vivo labelling experiments with fluorescein isothiocyanate ( FITC), FITC-labelled secondary antibodies, or proteinase K treatment r evealed that the anchored AbpS protrudes from the surfaces of the hyph ae. When we investigated the hydrophobicity of the deduced AbpS, one p utative transmembrane segment was predicted at the C terminus. By anal ysis of the secondary structure, a large centrally located alpha-helix which has weak homology to the tropomyosin protein family was found. Physiological studies shelved that AbpS is synthesized during the late logarithmic phase, independently of the carbon source.