The Structures and Functions of Antibodies

The major antibody in the serum is IgG and as this is the best-understood antibody in terms of structure and function we shall consider it shortly. The other antibody classes will then be considered in relation to IgG. First, however, a very brief overview of the structure and function of the different immunoglobulins will be presented [1],... 

Poly(ADP-ribose) synthetase is a chromatin-bound enzyme which, in the presence of DNA, catalyzes polymerization of the ADP-ribose moiety of NAD to form a protein-bound homopolymer, poly(ADP-ribose) (1). The enzyme is automodified during the reaction. It has been shown that the enzyme consists of three functional domains for DNA-binding, automodification, and NAD-binding (2-4). The enzyme has recently been purified from human placenta and characterized (4, 5). To study the structure and function of the enzyme in more detail we have prepared monoclonal antibodies to the placental enzyme (6, 7). The present study defines three monoclonal antibodies to human poly(ADP-ribose) synthetase and shows that one of the antibodies which binds to the NAD binding domain inhibits the enzyme activity. 

Various methods have been used in attempts to correlate the structure and function of the different cell components. Comparison of the fine structure of cells with differing functions shows that the number of mitochondria is correlated with metabolic activity and that the number of ribosomes relates to protein-synthesizing ability. Cytochemical techniques, including histochemistry, autoradiography and the use of fluorescent antibodies, have also contributed to our knowledge of the localization of particular enzymes, hormones and reactions. While these techniques have their limitations, they possess the great advantage that they cause little disturbance of the cell structure. On the other hand, cell fractionation techniques, which are widely used by biochemists, require the total disruption of cells. This is followed by the isolation and analysis of the released components. 

Burton, D. R. Structure and function of antibodies. In Molecular Genetics of Immunoglobulin (F. Calabi and M. S. Neuberger, eds.), Elsevier, Amsterdam, the Netherlands, 1987. 

H. Wade and T.S. Scanlan. 1997. The structural and functional basis of antibody catalysis Rev. Biophys. Biomol. Struct. 26 461-493. (PubMed)... 

The major selenium-containing plasma protein selenoprotein P can be determined by immunological methods. The production of monoclonal antibodies to selenoprotein P has been described and used to study tlie structure and function of the protein and to quantify it. It is also possible to separate selenoprotein P from other plasma proteins by heparin affinity chromatography followed by CFAAS selenium analysis. Selenoprotein P concentration in plasma responds rapidly to supplementation and has been used in nutritional studies of Chinese populations to confirm the adequacy of intake. "... 

A major area for new research concerns the structural and functional consequences of adsorption of proteins to surfaces (items 3-5 in Table IV). Measurement of conformational change is still in an early stage of development. Most methods for studying adsorbed protein conformation are restricted to comparison of spectral differences induced by adsorption, without knowledge of the actual type or amount of change these differences reflect. Better methodology, especially on quantitative aspects, is sorely needed in this area. The orientation of adsorbed proteins may prove to be readily explored with the monoclonal antibody method and therefore certainly deserves wider application. Finally, the behavior of enzymes and antibodies at interfaces is not... 

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