ANALYSIS OF DNA FLANKING THE XINB LOCUS OF STREPTOMYCES-LIVIDANS REVEALS GENES ENCODING ACETYL XYLAN ESTERASE AND THE RNA COMPONENT OF RIBONUCLEASE-P

Nucleotide sequencing revealed the gene (axeA) encoding acetyl xylan e sterase (AxeA) downstream from xlnB in the Streptomyces lividans DNA i nsert of plasmid pIAF42. AxeA consists of a catalytic- and a substrate -binding domain separated by a Gly-rich linker. The N terminus showed no significant homology with published esterases and acetyl xylan este rases, but some homology was found with the xylanases XylA and XylD an d the NodB protein of Rhizobium species which is involved in the biosy nthesis of root nodulation factors. The C terminus of AxeA is highly h omologous to the C-termini of xylanases XlnB and TFXA, corresponding t o the xylan-binding domain of these enzymes. Furthermore, the RNaseP R NA component was found immediately upstream from xlnB gene.