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Nocardioides sp. strain MTD22 degraded atrazine, ametryn and atraton, as did Arthrobacter aurescens strain TC1 and Nocardioides sp. strain C190. These strains contain trzN, a gene coding for TrzN, triazine hydrolase showing a broad substrate range. However, Nocardioides sp. strain AN3 degraded only atrazine despite containing trzN. These differences in s-triazine degradation are presumed to be due to differences in the amino acid sequences of TrzNs. Consequently, 1371 nucleotides of the trzN coding sequences of strains AN3 and MTD22 were determined. Comparisons of the amino acid sequences of TrzNs indicated that three residues of strain AN3 (Thr(214), His(215) and Gln(241)) were distinct from those of the other three strains (Pro(214), Tyr(215) and Glu(241)). To confirm the relationships between these amino acid sequences and the substrate specificities of TrzNs, wild and chimera trzN genes were constructed and expressed in Escherichia coli cells. Cells expressing wild MTD22 trzN (Pro(214)Tyr(215)Glu(241)) and chimera AN3-MTD22 trzN (Thr(214)His(215)Glu(241)) degraded all s-triazines, but the degradation rate was markedly decreased in AN3-MTD22 trzN. Wild AN3 trzN (Thr(214)His(215)Gln(241)) and chimera MTD22-AN3 trzN (Pro(214)Tyr(215)Gln(241)) degraded only atrazine. These results suggest that the substitution of Glu(241) for Gln(241) significantly decreases enzyme affinity for ametryn and atraton.

An inhibitor of blood coagulation, a new protein with an apparent molecular weight of 34,000 and an isoelectric point of 4.9, was purified from human placental tissue by EDTA extraction. Five cDNA clones were isolated from the human placental lambda gt11 cDNA library using the mouse monoclonal antibody raised against the coagulation inhibitor as the probe. The longest insert consists of 1,566 nucleotides, and contains 960 nucleotides entirely encoding the 320 amino acids of the inhibitor, and a poly A tail. The deduced amino acid sequence was corroborated by chemical analyses of the protein. The entire amino acid sequence shows homology to those of lipocortin I, lipocortin II, and endonexin-related proteins. The cDNA for the inhibitor was expressed in Escherichia coli under the regulation of the trc promotor of the plasmid pKK233-2. The resulting recombinant protein manifested inhibitory activities against both blood coagulation and phospholipase A2 activity, as did the coagulation inhibitor isolated from human placenta.