Protein structure in relation to function and biosynthesis.

TLDR: The chapter presents the outline of strategy that summarizes the approaches to sequence determination most generally followed and explores the partial hydrolysis of proteins.

Abstract: Publisher Summary The chapter discusses the protein structure in relation to function and biosynthesis. The chapter presents the outline of strategy that summarizes the approaches to sequence determination most generally followed. The sequence of individual protein chains appears to be best studied by the isolation and characterization of fragments produced by proteolytic digestion. The chapter explores the partial hydrolysis of proteins. Partial acid hydrolysis is probably useful mainly for the subsequent study of the larger peptide fragments produced by proteolysis. Sequence studies on proteins and peptides are dependent upon the isolation and characterization of residues or small groups of residues occupying definite positions in the peptide chain. The two unique residues in a peptide (except in cyclic compounds such as gramicidin) are those possessing a free amino group (the N -terminal residue) and those possessing a free α-carboxyl group (the C -terminal residue). These can be identified by suitable labeling techniques or by enzymatic methods. The determination of the nature of disulfide bridges in the insulin molecule has been described. Methods for the production and isolation of these bridges from proteins are quite empirical, and their successful application depends to a large degree on the chemical nature of the molecule under investigation. The approximate assignment of amide nitrogen to specific dicarboxylic amino acids in the sequence of a protein chain may be made on the basis of direct analyses for ammonia in hydrolyzates of peptides isolated from partial digests of such chains. This approach to the problem is a laborious one and may often not permit unequivocal assignments. The structure of individual proteins is also discussed.