Natural Polymers Proteins and Enzymes

The total annual output of papers written by protein biochemists is prodigious. This review covers the years 1979 and 1980 but it is neither comprehensive nor is it intended to be. The aim of this Chapter is to describe a selection of the current approaches and techniques which are being successfully applied to the study of protein structure and function. The emphasis is on progress rather than on the consolidation of factual knowledge, although the choice of the papers cited is inevitably coloured by the interests and prejudices of the author. It is hoped that the work included will give the non-specialist reader a feel for the current trends in different aspects of protein research and provide access to an unfamiliar literature. 

An ingeniously simple electrophoretic purification method has been described by Goldman and Baptist. Substantial purification was obtained by performing preparative gel electrophoresis at the pi of the protein under purification. The contaminating proteins migrate leaving the purified protein in the electrophoresis well, in high yield. 

As well as net charge, the surface hydrophobicity of proteins is another variable biophysical property that can be exploited in protein purification. Direct phase partition between aqueous solutions and dextran/polyethylene glycol has been used to separate two proteins with very similar charge properties and similar molecular weights (rat cr-foetoprotein and serum albumin). Similarly, cytochrome bjs, from chromaffin granule membranes, solubilized in octaethyleneglycol dodecylether and sodium cholate, could be separated from 50% saturated ammonium sulphate as a distinct viscous layer when the pH was dropped to 5.6. Denaturation at liquid-liquid interfaces usually precludes the use of this type of experiment in most applications. 

Hydrophobic partitioning is, however, exploited in a variety of colunrn techniques. Shiman et al achieved a high purification of L-phenylalanine 4-monoxygenase (E.C. 1.14.16.1) by what can essentially be described as biospecific retention on a hydrophobic chromatographic matrix. In the presence of L-phenylalanine the enzyme bound strongly to phenyl-agarose but desorbed when the column was washed with buffer, free of the amino-acid. 

Affinity chromatography is particularly valuable in the purification of proteins that interact with other macromolecules. Thus calmodulin-agarose has been used to 

Two factors, their biological importance and the complexity of their structures, have ensured the intensive study of proteins over many years, and this study has often involved multi-disciplinary approaches. 

In this Report, no attempt will be made to present a comprehensive review of all the work reported on the chemistry of proteins during the two years under consideration. Such an approach would be undesirable even if it were not impossible for a section of this length - about 10 000 references on amino-acids, peptides, and proteins are abstracted each year.  

Inevitably, references quoted in this Report will be, on the whole, simply illustrative examples, intended to convey to the reader the type of research being carried out and the kinds of information being obtained. For a detailed background to the whole subject of protein chemistry, readers are referred to the Specialist Periodical Reports on Amino-acids, Peptides, and Proteins, Volume 9 of which covers the literature published in 1976. All the enzymes mentioned in 

1 Amino-acid, Peptide, and Protein Abstracts, Volumes 6 and 7, Information Retrieval Ltd., London, 1977,1978. 

Novak-Hofer and P.-A. Siegenthaler, Biochim. Biophys. Acta, 1977,468, 461. 

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Natural Polymers Proteins and Enzymes 6 Conformational Structure... 

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