Mitochondrial carbonic anhydrase CA VB: Differences in tissue distribution and pattern of evolution from those of CA VA suggest distinct physiological roles
Mitochondrial carbonic anhydrase CA VB: Differences in tissue distribution and pattern of evolution from those of CA VA suggest distinct physiological roles
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DOI：
10.1073/pnas.97.4.1677
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发表时间：
2000-02-15
影响因子：
11.1
通讯作者：
Sly, WS
中科院分区：
文献类型：
--
作者：
Shah, GN;Hewett-Emmett, D;Sly, WS
另一种小鼠线粒体碳酸酐酶（CA）的cDNA称为CA VB，与先前鉴定的小鼠CA V（现在称为CA VA）具有同源性，全长cDNA编码一个317-aa前体，包含一个33-aa的经典线粒体先导序列。比较小鼠CA VB和CA VA在COS细胞中表达的cdna产物，发现两者都表达了位于线粒体中的活性CAs，并且在转染COS细胞的粗提物和分离的线粒体中表现出相当的活性。小鼠组织总rna的Northern blot分析和小鼠组织匀浆的Western blot分析显示，CA VB和CA VA在组织特异性表达上存在差异。CA VB在大多数组织中都很容易检测到，而CA VA的表达仅限于肝脏、骨骼肌和肾脏。最近也报道了小鼠CA - VB的人同源性。将人CA VB的CA域序列与本文报道的CA域序列进行比较，发现CA VB的CA域在小鼠和人之间的保守性（95%的一致性）远高于小鼠和人CA VAs的CA域（78%的一致性）。对这些同工酶序列与其他人类和小鼠CA同工酶序列的系统发育关系分析显示，哺乳动物CA VB比CA VA进化得慢得多，接受氨基酸替换的速度至少慢4.5倍，因为它们都是在大约9000万年前从各自的人类小鼠祖先基因进化而来的。CA - VB序列在组织分布上的差异和更大的进化限制表明，CA - VB和CA - VA已经进化到承担不同的生理作用。
A cDNA for a second mouse mitochondrial carbonic anhydrase (CA) called CA VB was identified by homology to the previously characterized murine CA V, now called CA VA. The full-length cDNA encodes a 317-aa precursor that contains a 33-aa classical mitochondrial leader sequence. Comparison of products expressed from cDNAs for murine CA VB and CA VA in COS cells revealed that both expressed active CAs that localized in mitochondria, and showed comparable activities in crude extracts and in mitochondria isolated from transfected COS cells. Northern blot analyses of total RNAs from mouse tissues and Western blot analyses of mouse tissue homogenates showed differences in tissue-specific expression between CA VB and CA VA. CA VB was readily detected in most tissues, while CA VA expression was limited to liver, skeletal muscle, and kidney. The human orthologue of murine CA VB was recently reported also. Comparison of the CA domain sequence of human CA VB with that reported here shows that the CA domains of CA VB are much more highly conserved between mouse and human (95% identity) than the CA domains of mouse and human CA VAs (78% identity). Analysis of phylogenetic relationships between these and other available human and mouse CA isozyme sequences revealed that mammalian CA VB evolved much more slowly than CA VA, accepting amino acid substitutions at least 4.5 times more slowly since each evolved from its respective human-mouse ancestral gene around 90 million years ago. Both the differences in tissue distribution and the much greater evolutionary constraints on CA VB sequences suggest that CA VB and CA VA have evolved to assume different physiological roles.