Structural homologies in alanine-rich acidic ribosomal proteins from procaryotes and eucaryotes

Abstract

The amino acid composition and amino[N]-terminal sequence were determined for the alanine-rich, acidic ribosomal A protein (equivalent to Escherichia coli L7/L12) from 3 prokaryotic cell types that live under extreme environmental conditions (Arthrobacter glacialis, Clostridium pasteurianumand Bacillus stearothermophilus) and from wheat germ, a eukaryote source. These data are compared with previously published A protein sequences from other prokaryotes and eukaryotes. All the prokaryotic A proteins, with the exception of the very acidic A protein from Halobacterium cutirubrum, show similar charge size and amino acid composition, and an extensive sequence homology in the N-terminal region. Some difference were observed between gram-negative and gram-positive bacteria. The A proteins from eukaryotes contain 2 tyrosine molecules, an amino acid absent in prokaryotic A proteins, and a reduced number of valine residues and an increased amount of aspartic acid. The N-terminal sequence of wheat germ A protein shows considerable homology with other eukaryotic A proteins and also with H. cutirubrum. It also shows some sequence homology with E. coli A proteins.