ABSTRACT
Artificial ribonucleases, conjugates of short oligodeoxyribonucleotides and peptides built of arginine, leucine, proline, and serine, were synthesized and assessed in terms of ribonuclease activity and specificity of RNA cleavage. A specific group of the conjugates was identified that display T1-ribonuclease-like activity and cleave RNA predominantly at G-X sequences. Circular dichroism study of the structures of the most active conjugates, free peptide (LR)4G, and oligonucleotides revealed that conjugation of oligonucleotide to the peptide results in a specific peptide folding that possibly provides ribonuclease activity to the conjugate.
Subject(s)
Guanine/chemistry , Oligodeoxyribonucleotides/chemistry , Oligopeptides/chemistry , Oligopeptides/metabolism , RNA , Ribonucleases , Base Pairing , Circular Dichroism , Nucleic Acid Conformation , RNA/chemistry , RNA/metabolism , Ribonucleases/chemistry , Ribonucleases/metabolism , Substrate SpecificityABSTRACT
It was shown for the first time that a small fraction of milk secretory IgA (sIgA) is tightly bound to oligosaccharides (oligoSACs) and polysaccharides (polySACs). The ability of sIgA to phosphorylate oligo- and polysaccharides was shown to be an intrinsic property of this antibody. In contrast to known kinases, sIgAs with polysaccharide kinase activity can transfer phosphoryl group to oligo- and polysaccharides not only from [gamma-(32)P]ATP but can also use [(32)P]orthophosphate as a substrate of phosphorylation reaction. An extremely unusual property of polysaccharide kinase Abs is their high affinity for orthophosphate (K(m) = 15-77 microM), and orthophosphate is a better substrate than ATP. Two first examples of natural abzymes (Abzs) with synthetic activity were milk sIgA with protein and lipid kinase activities. Polysaccharide kinase sIgA of human milk is the third example of natural antibodies (Abs) with synthetic activity.
