[Endonuclease activity of recombinant pancreatic nuclease (A-K7H)].
Pancreatic ribonuclease A (RNase A) is a endonuclease that catalyzes depolymerization of ribonucleic acid (RNA) releasing oligonucleotides. In the process of binding enzyme with substrate are involved several non-catalytic phosphate binding subsites, one of them is p2, additional to main catalytic site p1. RNaza A prefers binding and cleavage of longer substrate molecules, and 3',5'-phosphodiester bond should be some six-seven residues apart from the end of molecules of the chain of RNA. In this work is analysed endonuclease activity of recombinant pancreatic RNase A (K7H), that in position seven instead of a lysine there is a histidine, amino acid residue that participates in main catalytic site p1. Mutant enzyme is obtained by site-directed mutagenesis by Kunkel. Results of this investigation have shown that substitution of lysine by histidine in position seven of RNase A has produced total deletion of p2 subsite, and K7H has lost endonuclease activity, and has become exonuclease. These results confirm central role of Lys-7 in establishing p2 subsite and endonuclease activity of pancreatic RNase A.
Ljuca
F
F
Zavod za fiziologiju, Medicinski fakultet Tuzla, Univerzitet Tuzla.
Moussaoui
M
M
Boix
E
E
Nogues
V
V
Ljuca
D
D
Cuchillo
C M
CM
D019943:Amino Acid Substitution; D016297:Mutagenesis, Site-Directed; D011994:Recombinant Proteins / Q000737:chemistry; D012259:Ribonuclease, Pancreatic / Q000737:chemistry*
D011994:Recombinant Proteins; D012259:Ribonuclease, Pancreatic
Endonukleazna aktivnost rekombinantne pankreasne ribonukleaze A-K7H.