Department of Microbiology and Biotechnology, College of Life Sciences, Northeast Agricultural University, No. 600 Changjiang Road, Xiangfang District, Harbin 150030, China.
Department of Microbiology and Biotechnology, College of Life Sciences, Northeast Agricultural University, No. 600 Changjiang Road, Xiangfang District, Harbin 150030, China.
J Mol Biol. 2021 Jan 22;433(2):166730. doi: 10.1016/j.jmb.2020.166730. Epub 2020 Dec 3.
Na/Hantiportersare a category of ubiquitous transmembrane proteins with various important physiological roles in almost all living organisms ranging from bacteria to humans. However, the knowledge of novel Na/Hantiporters remains to be broadened, and the functional roles ofoligomerization in theseantiportershave not yet been thoroughly understood. Here, we reported functional analysis of an unknown transmembrane protein composed of 103 amino acid residues. This protein was found to function as a Na(Li, K)/H antiporter. To the best of our knowledge, this antiporter is the minimal one of known Na/Hantiporters and thus designated as NhaM to represent the minimal Na/Hantiporter. NhaM and its homologs have not yet been classified into any protein family. Based on phylogenetic analysis and protein alignment, we propose NhaM and its homologs to constitute a novel transporter family designated as NhaM family. More importantly, we found that NhaM is assembled with parallel protomers into a homo-oligomer and oligomerization is vital for the function of this antiporter. This implies that NhaM may adopt and require an oligomer structure for its normal function to create a similar X-shaped structure to that of the NhaA fold. Taken together, current findings not only present the proposal of a novel transporter family but also positively contribute to the functional roles of oligomerization in Na/Hantiporters.
钠氢反向转运蛋白是一类普遍存在的跨膜蛋白，在从细菌到人类的几乎所有生物体中具有多种重要的生理功能。然而，新型钠氢反向转运蛋白的知识仍有待拓宽，这些转运蛋白的寡聚化的功能作用尚未被完全理解。在这里，我们报道了由 103 个氨基酸残基组成的未知跨膜蛋白的功能分析。该蛋白被发现具有 Na(Li，K)/H 反向转运蛋白的功能。据我们所知，这种反向转运蛋白是已知的钠氢反向转运蛋白中最小的一种，因此被命名为 NhaM，代表最小的钠氢反向转运蛋白。NhaM 和它的同源物尚未被归类为任何蛋白质家族。基于系统发育分析和蛋白质比对，我们提出 NhaM 和它的同源物构成了一个新的转运蛋白家族，命名为 NhaM 家族。更重要的是，我们发现 NhaM 与平行的蛋白亚基组装成同源寡聚体，寡聚化对于该反向转运蛋白的功能至关重要。这意味着 NhaM 可能采用并需要一个寡聚体结构来发挥其正常功能，从而形成类似于 NhaA 折叠的类似 X 形结构。总之，目前的研究结果不仅提出了一个新的转运蛋白家族的建议，而且对钠氢反向转运蛋白的寡聚化功能作用也做出了积极贡献。
