C2 - Posttranslational Modification of Membrane Proteins

Abstract

This chapter deals with modifications of specific mycoplasma membrane proteins, established especially by metabolic labeling with radioactive isotopes. The individual amino acid residues in proteins can be chemically modified in vivo in many different ways. Information for many modifications and processing sites reside in the amino acid sequence. This is also the case for a variety of binding motifs and domains. The recent PROSITE compilation of such sites and patterns, available in several molecular biology computer programs, lists more than 800 different patterns. The biological occurrence, recognition, and chemical analysis of many of these have been described. Compared to extensively studied bacteria such as Escherichia coli, little has been done in the field of membrane protein modification in mycoplasmas. Covalent modification of mycoplasma membrane proteins are conventionally detected by one-dimensional slab gels. In bacteria, a specific target sequence specifies signal peptide cleavage and a consecutive modification of the new N-terminal cysteine residue with one ether-bonded glycerol carrying two ester-linked acyl chains and one amide-linked alkyl chain at the Cys amino group.