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Ribonucleases (RNases) constitute a cellular function of exo- and endo-nucleases in all living organisms include vertebrate, bacteria, mold and plant. Human ribonuclease A (hRNaseA) super family consists of thirteen members with high structure similarities. Among which hRNase3 has multiple functions such as RNase, cytotoxicity, and heap ran sulfate (HS) binding activity. Employing Clustal W2 multiple sequence alignment of 13 human RNase A family members revealed that hRNase3 shares 67% identity and 76% similarity with hRNase2, much higher than the others. Besides, both RNase 2 and RNase3 are high conserved among primates. In terms of hRNase3-heparin/heparan sulfate (HS) interaction, three putative heparin binding regions (HBRs), 34RWRCK38 (HBR1), 75RSRFR79 (HBR2) and 101RPGRR105 (HBR3) have been predicted due to presence of positive charge clusters. Furthermore, these regions are also characterized as unique peptide regions within all 13 RNase sequences by REMUS system. Our experimental data derived from protein engineering and binding assays have demonstrated that these HBRs indeed involve in characteristic functions of hRNase3. In summary, through evolution hRNaseA super family has gained novel functions which may be preserved in the unique region or domain to account for additional molecular interactions. [ABSTRACT FROM PUBLISHER]

Human ribonuclease A (hRNaseA) super family members have similar biological functions such as catalytic activities against specific RNA substrates. However, these enzymes with high sequence similarity may exhibit divergent physiological functions other than RNase activity, for example, angio genesis and innate immunity. In our investigation, a novel heparin-binding motif (HBM), RWRCK, identified from hRNase3 contributed to specific protein-heparin/heparan sulfate (HS) interaction. Based on this core HBM sequence, a 10-amino acid heparin binding peptide (HBPRNase3), NYRWRCKNQN, has been designed and characterized. Employing Clustal W2 and Uniprot Blastn program, such HBP pattern is found to be conserved in human and higher primates. Multiple sequence alignment of 13 members of human RNase A family reveals that HBP regions in hRNase2 and hRNase8 share 80% and 50% sequence identity to HBPRNase3, but the corresponding sequences of Gorilla and Pan troglodytes RNase3 are 100% identical, strongly suggesting that HBPRNase3 is conserved in higher primates along with species evolution. Interestingly, the putative HBPRNase2, NYQRRCKNQN, shows much lower heparin binding activity than HBPRNase3. In summary, HBPRNase3 is not a conserved motif in RNase A super family, but it is a unique motif presenting in higher primates to play a crucial role in molecular interaction to heparin and HS. [ABSTRACT FROM PUBLISHER]