Calcium-dependent endoribonuclease of Trypanosoma brucei has a base-preferential affinity to adenylate
Gbenle, G.O.
Biochemistry International 10(2): 241-250
1985
ISSN/ISBN: 0158-5231 PMID: 2581576 Document Number: 248127
The substrate specificity of a calcium-dependent endoribonuclease of T. brucei cytoplasm was determined. The actions of the enzyme on transfer RNA, ribosomal RNA and various synthetic polyribonucleotides indicate that the enzyme degrades double-stranded as well as single-stranded RNAs; it preferentially hydrolyses polyribonucleotides having adenylic acid residues, and has a pronounced preference for poly (adenylic acid). Its apparent Michaelis constant (Km) values using different substrates also suggest a base-preferential affinity of the enzyme to adenylate. The relative activity of the ribonuclease against homopolyribonucleotides is poly(A) > poly(U) > poly(C); poly(G) is completely resistant to the activity. Poly(A) segments on poly(A)-rich RNA are selectively hydrolyzed by the endoribonuclease. A possible implication of this enzyme in the post-transcriptional modification and turnover of mRNA molecules is suggested.