The retinal rod Na+/Ca2+,K+ exchanger contains a noncleaved signal sequence required for translocation of the N terminus

被引:6
作者
McKiernan, CJ [1 ]
Friedlander, M [1 ]
机构
[1] Scripps Res Inst, Dept Cell Biol, La Jolla, CA 92037 USA
关键词
D O I
10.1074/jbc.274.53.38177
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
The retinal rod Na+/Ca2+,K+ exchanger (RodX) is a polytopic membrane protein found in photoreceptor outer segments where it is the principal extruder of Ca2+ ions during light adaptation. We have examined the role of the N-terminal 65 amino acids in targeting, translocation, and integration of the RodX using an in vitro translation/translocation system, cDNAs encoding human RodX and bovine RodX through the first transmembrane domain were correctly targeted and integrated into microsomal membranes; deletion of the N-terminal 65 amino acids (aa) resulted in a translation product that was not targeted or integrated. Deletion of the first 65 aa had no effect on membrane targeting of full-length RodX, but the N-terminal hydrophilic domain no longer translocated. Chimeric constructs encoding the first 65 aa of bovine RodX fused to globin were translocated across microsomal membranes, demonstrating that the sequence could function heterologously. Studies of fresh bovine retinal extracts demonstrated that the first 65 aa are present in the native protein. These data demonstrate that the first 65 aa of RodX constitute an uncleaved signal sequence required for the efficient membrane targeting and proper membrane integration of RodX.
引用
收藏
页码:38177 / 38182
页数:6
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