The importance of a single amino acid substitution in reduced red blood cell carbonic anhydrase function of early-diverging fish
The importance of a single amino acid substitution in reduced red blood cell carbonic anhydrase function of early-diverging fish
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单一氨基酸替代对早期分化鱼红细胞碳酸酐酶功能降低的重要性
DOI：
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
A. Esbaugh
中科院分区：
文献类型：
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作者：
Angelina M. Dichiera;Olivia J. L. McMillan;Alexander M. Clifford;G. Goss;C. Brauner;A. Esbaugh
在大多数脊椎动物中，红细胞碳酸酐酶（RBC CA）在二氧化碳（CO2）在上皮组织中的运输和排泄中起着关键作用。许多早期分化的鱼类（如盲鳗和软骨鱼）在鳃中具有可进入血浆的膜结合CA-IV是独一无二的，这使得一些二氧化碳的排泄在没有红细胞参与的情况下发生。然而，这对RBC CA功能的影响尚不清楚。通过同源克隆技术，我们从9个早期分化物种中鉴定出推测的RBC CA蛋白序列。在所有情况下，这些序列都包含质子穿梭残基His-64的修饰，并且对三条早期分化鱼的活性测量表明，CA活性显著降低。利用定点突变恢复His-64质子穿梭，显著提高了红细胞CA活性，清楚地说明了His-64在鱼红细胞CA活性中的功能意义。对55种脊椎动物细胞质CA同工酶的贝叶斯分析表明，独立的进化事件导致His-64的修饰，从而降低了盲鳗和软骨鱼的CA活性。此外，在具有鳃CA-IV的早期分化鱼类中，红细胞ca中缺乏His-64，也没有根效应（pH值降低会降低血红蛋白与氧气结合的能力）。综上所示，这些数据表明，低活性的红细胞CA可能存在于所有具有鳃CA- iv的鱼类中，而在大多数硬骨鱼中看到的高活性红细胞CA可能与血红蛋白pH敏感性增强一起进化。
In most vertebrates, red blood cell carbonic anhydrase (RBC CA) plays a critical role in carbon dioxide (CO2) transport and excretion across epithelial tissues. Many early-diverging fishes (e.g., hagfish and chondrichthyans) are unique in possessing plasma-accessible membrane-bound CA-IV in the gills, allowing some CO2 excretion to occur without involvement from the RBCs. However, implications of this on RBC CA function are unclear. Through homology cloning techniques, we identified the putative protein sequences for RBC CA from nine early-diverging species. In all cases, these sequences contained a modification of the proton shuttle residue His-64, and activity measurements from three early-diverging fish demonstrated significantly reduced CA activity. Site-directed mutagenesis was used to restore the His-64 proton shuttle, which significantly increased RBC CA activity, clearly illustrating the functional significance of His-64 in fish red blood cell CA activity. Bayesian analyses of 55 vertebrate cytoplasmic CA isozymes suggested that independent evolutionary events led to the modification of His-64 and thus reduced CA activity in hagfish and chondrichthyans. Additionally, in early-diverging fish that possess branchial CA-IV, there is an absence of His-64 in RBC CAs and the absence of the Root effect [where a reduction in pH reduces hemoglobin’s capacity to bind with oxygen (O2)]. Taken together, these data indicate that low-activity RBC CA may be present in all fish with branchial CA-IV, and that the high-activity RBC CA seen in most teleosts may have evolved in conjunction with enhanced hemoglobin pH sensitivity.
哺乳动物碳酸酐酶的遗传学。
影响因子：
--
作者：
Tashian,RE
通讯作者：
Tashian,RE
影响因子：
2.9
作者：
TU, CK;SILVERMAN, DN;LINDSKOG, S
通讯作者：
LINDSKOG, S