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Determinants of action of phospholipases A2 on the envelope phospholipids of Escherichia coli

Thesis/Dissertation ·
OSTI ID:5179838
The rabbit neutrophil phospholipase A2 (PLA2) degrades the phospholipids of E. coli killed by a bactericidal protein purified from the rabbit neutrophil. Of nine other PLA2 examined four were inactive, four produced low levels of hydrolysis, and one, the basic isozyme of the Agkistrodon halys blomhoffii venom, was very active. Because of the highly cationic properties of the basic Agkistrodon PLA2(pl = 10.2) the author examined the role of net positive charge in the ability of the PLA2 to act on the phospholipids of E. coli. Lysines in the basic venom PLA2 were chemically modified using two procedures, reductive methylation and carbamylation. Modification of up to 4 Lys/molecule did not alter catalytic activity as measured by using artificial substrates. In contrast, the ability of the basic PLA2 to act on E. coli exposed to the bactericidal protein was reduced by 70% when 1 Lys/molecule had been modified. The primary sequence of the basic PLA2 was determined and the specific radioactivity of individual carbamylated lysines was measured when 1 mol of (14C)cyanate/mol of protein had been incorporated. X-ray structure analysis by others of 3 PLA2 and secondary structure reductions of 30 PLA2, including the basic PLA2, indicate that the first 13 residues of the basic PLA2 are arranged in an alpha helical conformation.
Research Organization:
New York Univ., NY (USA)
OSTI ID:
5179838
Country of Publication:
United States
Language:
English