A modular domain of NifU, a nitrogen fixation cluster protein, is highly conserved in evolution

被引:38
作者
Hwang, DM
Dempsey, A
Tan, KT
Liew, CC
机构
[1] UNIV TORONTO,TORONTO HOSP,DEPT CLIN BIOCHEM,MOL CARDIOL LAB,CTR CARDIOVASC RES,TORONTO,ON,CANADA
[2] UNIV TORONTO,TORONTO HOSP,DEPT MED,MOL CARDIOL LAB,CTR CARDIOVASC RES,TORONTO,ON,CANADA
关键词
nitrogen fixation cluster; nifU gene; cDNA sequence;
D O I
10.1007/PL00006114
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
hnifU, a gene exhibiting similarity to nifU genes of nitrogen fixation gene clusters, was identified in the course of expressed sequence tag (EST) generation from a human fetal heart cDNA library. Northern blot of human tissues and polymerase chain reaction (PCR) using human genomic DNA verified that the hnifU gene represented a human gene rather than a microbial contaminant of the cDNA library. Conceptual translation of the hnifU cDNA yielded a protein product bearing 77% and 70% amino acid identity to NifU-like hypothetical proteins from Haemophilus influenzae and Saccharomyces cerevisiae, respectively, and 40-44% identity to the N-terminal regions of NifU proteins from several diazatrophs (i.e., nitrogen-fixing organisms). Pairwise determination of amino acid identities between the NifU-like proteins of nondiazatrophs showed that these NifU-like proteins exhibited higher sequence identity to each other (63-77%) than to the diazatrophic NifU proteins (40-48%). Further, the NifU-like proteins of non-nitrogen-fixing organisms were similar only to the N-terminal region of diazatrophic NifU proteins and therefore identified a novel modular domain in these NifU proteins. These findings support the hypothesis that NifU is indeed a modular protein, The high degree of sequence similarity between NifU-like proteins from species as divergent as humans and H. influenzae suggests that these proteins perform some basic cellular function and may be among the most highly conserved proteins.
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页码:536 / 540
页数:5
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