Structure of the <i>Escherichia coli</i> ThiS−ThiF Complex, a Key Component of the Sulfur Transfer System in Thiamin Biosynthesis^,

Abstract

Different methods of separation of mitochondrial polyribosomes of the yeast Saccharomyces cerevisiae from the admixtures of cytoplasmic polyribosomes firmly bound to the outer mitochondrial membrane has been carried out. It has been shown that treatment of mitochondria with 0.5 M KCl -- 1 mM puromycin alone allows to obtain a highly purified fraction of mitochondrial polyribosomes (Sw, 20 = 100--200S), consisting of 2--3 monomers. Gel-filtration under denaturing conditions of nascent polypeptides bound to mitochondrial polyribosomes has revealed a predominance of polypeptides with molecular weights of 10000--11000. Isoelectrofocusing of labelled polypeptides in the presence of ampholines (pH 3--10) has demonstrated that they are predominantly focussed in the pH region around 9.0 and, consequently, possess basic properties.