博士 / 國立臺灣大學 / 生化學研究所 / 88 / Approximately 95% of the amino acid sequence of a shrimp (Penaeus japonicus) nuclease, previously designated as DNase I, was derived from the sequences of protease-digested peptides. The cDNA for the nuclease was amplified using primers synthesized based on the amino acid sequence. The amplified fragments shown to be a 1461-base cDNA containing an open reading frame encoding a putative 21-residue signal peptide and a 381-residue mature protein. The composition and MALDI-TOF mass analyses of a tryptic peptide suggested that the NH2-terminus of the mature enzyme was pyroglutamate, confirmed by a glutamine residue in the cDNA encoded sequence. The enzyme, without free sulfhydryl groups, contained eleven half-Cys residues, ten of which formed five intra-molecular disulfides and the eleventh residue at position 101 was linked to a 604 Da thiol compound. A sequence similarity search revealed no homologous proteins in the databases. However, residues 205-255 shared a significant similarity to a conserved motif in a distinct group of nucleases, in which the ArgGlyHis89 tripeptide in the Serratia nuclease active site corresponded to LysGlyHis211 in shrimp nuclease. Site specific modification with iodoacetate further supported involvement of His211 in catalysis. The purified shrimp nuclease was shown to possess a low level of hydrolytic activity toward RNA in the presence of Mg2+ and Ca2+. Conservation of functionally important residues during distant evolution may imply that the catalytic mechanisms are similar in these nucleases which should be classified in one subfamily.
| Identifer | oai:union.ndltd.org:TW/088NTU01104004 |
| Date | January 2000 |
| Creators | Wang, Wen-Yi, 王文綺 |
| Contributors | Liao, Ta-Hsiu, 廖大修 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 168 |
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