The pur8 gene from the pur cluster of Streptomyces alboniger encodes a highly hydrophobic polypeptide which confers resistance to puromycin

Abstract

A novel puromycin-resistance determinant (pur8) was isolated from one end of the pur cluster that encodes the puromycin biosynthetic pathway from Streptomyces alboniger and expressed in Streptomyces lividans. The gene pur8 induced antibiotic resistance that was highly specific for puromycin. The nucleotide sequence of pur8 contains an open reading frame of 1512 bp whose deduced amino acid sequence encodes a polypeptide (Pur8) with 14 possible transmembrane-spanning segments. It shows significant similarities to other known or putative transmembrane proteins, including a number which confer drug resistance in a variety of antibiotic-producing Streptomyces, Gram-positive and Gram-negative bacteria, and some solute transporters of prokaryotic and eukaryotic origin. As is probably the case for most of these proteins, Pur8 may be involved in active puromycin efflux energized by a proton-dependent electrochemical gradient. In addition, it could be implicated in secreting N-acetylpuromycin, the last intermediate of the biosynthesis pathway, to the environment.