Zhang Han, Rahman Sadia, Li Wen, Fu Guoxing, Kaur Parjit
Department of Biology, Georgia State University, Atlanta, GA, 30303, USA.
Department of Biology, Georgia State University, Atlanta, GA, 30303, USA.
Biochem Biophys Res Commun. 2015 Mar 27;459(1):148-53. doi: 10.1016/j.bbrc.2015.02.086. Epub 2015 Feb 24.
A novel domain, GATE (Glycine-loop And Transducer Element), is identified in the ABC protein DrrA. This domain shows sequence and structural conservation among close homologs of DrrA as well as distantly-related ABC proteins. Among the highly conserved residues in this domain are three glycines, G215, G221 and G231, of which G215 was found to be critical for stable expression of the DrrAB complex. Other conserved residues, including E201, G221, K227 and G231, were found to be critical for the catalytic and transport functions of the DrrAB transporter. Structural analysis of both the previously published crystal structure of the DrrA homolog MalK and the modeled structure of DrrA showed that G215 makes close contacts with residues in and around the Walker A motif, suggesting that these interactions may be critical for maintaining the integrity of the ATP binding pocket as well as the complex. It is also shown that G215A or K227R mutation diminishes some of the atomic interactions essential for ATP catalysis and overall transport function. Therefore, based on both the biochemical and structural analyses, it is proposed that the GATE domain, located outside of the previously identified ATP binding and hydrolysis motifs, is an additional element involved in ATP catalysis.
在ABC蛋白DrrA中鉴定出一个新结构域GATE（甘氨酸环和转导元件）。该结构域在DrrA的紧密同源物以及远缘相关的ABC蛋白中表现出序列和结构保守性。该结构域中高度保守的残基包括三个甘氨酸，即G215、G221和G231，其中发现G215对DrrAB复合物的稳定表达至关重要。其他保守残基，包括E201、G221、K227和G231，被发现对DrrAB转运蛋白的催化和转运功能至关重要。对先前发表的DrrA同源物MalK的晶体结构和DrrA的模拟结构进行的结构分析表明，G215与沃克A基序及其周围的残基紧密接触，这表明这些相互作用可能对维持ATP结合口袋以及复合物的完整性至关重要。还表明，G215A或K227R突变减少了一些对ATP催化和整体转运功能至关重要的原子相互作用。因此，基于生化和结构分析，有人提出位于先前确定的ATP结合和水解基序之外的GATE结构域是参与ATP催化的另一个元件。
