The carboxy terminus of the colonic H(+), K(+)-ATPase alpha-subunit is required for stable beta subunit assembly and function.
The carboxy terminus of the colonic H(+), K(+)-ATPase alpha-subunit is required for stable beta subunit assembly and function.
复制标题
结肠 H( )、K( )-ATP 酶 α 亚基的羧基末端是稳定 β 亚基组装和功能所必需的。
DOI：
10.1111/j.1523-1755.2004.00507.x
复制
发表时间：
2004
影响因子：
19.6
通讯作者：
DuBoseJr,ThomasD
中科院分区：
文献类型：
--
作者：
Li,Jian;Codina,Juan;Petroske,Elizabeth;Werle,MikeJ;DuBoseJr,ThomasD
The carboxy terminus of the colonic H+,K+-ATPase α-subunit is required for stable β subunit assembly and function.BackgroundThe present experiments were designed to study the importance of the carboxy-terminus of colonic H+,K+-ATPase α-subunit (HKα2), for both function as well as integrity of assembly with β1-Na+,K+-ATPase.MethodsFor this purpose, a mutation of 84 amino acids in the carboxy-terminus was created (ΔHKα2) and HEK-293 cells were used as expression systems for functional studies using86Rb+-uptake, coimmunoprecipitation using specific antibodies and fluorescence microscopy using green fluorescent protein.ResultsThe results demonstrate that comparable levels of expression of HKα2and ΔHKα2mRNA were observed when cells were cotransfected with β1subunit. However, the abundance of expression of full length HKα2protein exceeded that of the truncated protein ΔHKα2. Ouabain-sensitive86Rb+-uptake was present only in cells cotransfected with HKα2/β1, indicating that the mutation was incapable of sustaining functionality. Coimmunoprecipitation experiments demonstrated that HKα2protein was immunoprecipitated more abundantly than ΔHKα2when coexpressed with β1. The use of sucrose gradients and green fluorescence protein immunofluorescence demonstrated that while the ΔHKα2/β1complex was confined to the endoplasmic reticulum, the HKα2/β1complex translocated to the plasma membrane.ConclusionTaken together, our results are consistent with the view that the carboxy-terminus of HKα2facilitates the proper folding of the HKα2/β1complex allowing translocation of the heterodimer to the plasma membrane where potassium uptake occurs. Otherwise, the α/β complex is destined for degradation.
