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L M Chang

Publications and source records attributed to L M Chang.

66 records · Page 4Linked to original sources
PubMed1972

Antigenic relationships in mammalian DNA polymerase.

Rabbit antibody was prepared against a high-molecular-weight DNA polymerase purified from the soluble fraction of calf thymus gland. This antibody does not inhibit terminal deoxynucleotidyl transferase isolated from that source, but does inhibit both low-molecular-weight and high-molecular-weight DNA polymerases isolated from cytoplasmic and nuclear fractions of a number of mammalian tissues (mouse L cells, calf thymus, phytohemagglutinin-stimulated human lymphocytes, rat liver, and rabbit bone marrow). The results suggest that (i) no antigenic relationship exists between terminal transferase and DNA polymerase, (ii) common antigenic determinants exist in the DNA polymerases from all mammalian sources, and (iii) multiple forms of DNA polymerase found in mammalian, cells are related by having polypeptide sequences or subunits in common.

Animals↗
PubMed1970

Doxynucleotide-polymerizing enzymes of calf thymus gland. IV. Inhibition of terminal deoxynucleotidyl transferase by metal ligands.

The polymerization of deoxynucleoside triphosphates, catalyzed by terminal deoxynucleotidyl transferase from calf thymus gland, is strongly inhibited by various metal chelators. The reaction appears to be first order with respect to enzyme, deoxynucleoside triphosphate, and initiator, indicating that there is only one catalytic center for each enzyme molecule. The presence of metal chelator does not affect the molecular state of the enzyme or the order of reaction. An analysis of the kinetics of o-phenanthroline inhibition demonstrates that the ligand is noncompetitive with nucleoside triphosphate substrate and strictly competitive with oligodeoxynucleotide initiator. These results, obtained in the presence of millimolar Mg(++), suggest that the initiator binds to the enzyme through a transition metal atom and ligand inhibition occurs at that site. The precise spatial arrangement of the coordination orbitals around a metal atom provides a model to visualize the specificity of the enzyme for the 3'-OH end of the growing polynucleotide chain.

Animals↗