On a Salmon (Onchorhynchus keta) Liver RNase, Belonging to RNase T2 Family: Primary Structure and Some Properties

Zebrafish RNase T2 genes and the evolution of secretory ribonucleases in animals

“…Although early studies detected only faint RNase activity in fish organ extracts [ 18 ], an RNase T2 with acidic pH preference was recently isolated from salmon liver [ 19 ]. To identify RNase activities in zebrafish extracts we used a standard in gel activity assay that allows size separation of different proteins with RNase activity, as well as characterization of pH preference.…”

“…Thus, several bands in the RNase T2 range suggested that the zebrafish genome also contained more than one RNase T2 gene. A BLASTP [ 20 ] search against the protein prediction database of the current zebrafish genome assembly (Zv7) using the RNase Ok2 sequence from salmon [ 19 ] identified two proteins with homology to RNase T2 enzymes, one located in chromosome 15 and the other in chromosome 13. Additional searches using these two proteins (using TBLASTN), or the corresponding nucleotide sequences (using BLASTN) against the full genome assembly and available ESTs failed to identify any additional sequences corresponding to RNase T2 homologs.…”

“…The recent characterization of RNase Ok2 [ 19 ] showed that in this protein, a commonly conserved His residue in CAS II (His104 in RNase Rh, Tyr102 in RNase Dre2) is mutated to Tyr. This change most likely affects the catalytic properties of the enzyme and results in lower specific activity [ 19 ].…”

Enzymatic Properties of Serine 93 Mutants of RNase Rh from Rhizopus niveus. A Trial to Alter the Base Preference of RNase Rh

“…This finding forced us to reconsider the role of His104, and we proposed a new mechanism. 13) In this mechanism, we suggested that His104 is not only important for phosphate binding on a substrate, it is also crucial to the exhibition of high enzymatic activity by stabilization of a pentacovalent intermediate.…”

“…4,12) The other amino acid residues probably work to stabilize the pentacovalent intermediate. 1) Very recently we determined the primary structure of an RNase from salmon liver (RNase Ok2), 13) in which the His104 (RNase Rh numbering) was replaced by tyrosine residue and showed very low enzyme activity (about 5%) compared to the other members of RNases, such as RNase Rh. This finding forced us to reconsider the role of His104, and we proposed a new mechanism.…”