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首页> 外文期刊>Biochemistry >MUTATION OF CONSERVED RESIDUES IN TRANSMEMBRANE DOMAINS 4, 6, AND 8 CAUSES LOSS OF CA2+ TRANSPORT BY THE PLASMA MEMBRANE CA2+ PUMP
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MUTATION OF CONSERVED RESIDUES IN TRANSMEMBRANE DOMAINS 4, 6, AND 8 CAUSES LOSS OF CA2+ TRANSPORT BY THE PLASMA MEMBRANE CA2+ PUMP

机译：跨膜域4、6和8中保留残基的突变导致血浆膜CA2 +泵的CA2 +运输损失

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摘要

Mutants of the plasma membrane Ca2+ pump (PMCA), in which amino acids in transmembrane domains (TM) 4, 6, and 8 had been replaced, have been expressed in COS-7 cells. They were analyzed functionally by measuring the uptake of Ca2+ in microsomal preparations and by following the formation of the phosphorylated intermediate from ATP and from phosphate. The mutated residues corresponded to amino acids whose mutation in the sarcoplasmic reticulum pump (SERCA) caused loss of Ca2+ transport by the pump protein: however, only four of the six SERCA residues were conserved in the PMCA pump. Mutation of Glu423 (TM4), Asn879 or Asp883 (TM6), or Gln971 (TM8) suppressed Ca2+ transport by the pump and its ability to form the phosphorylated intermediate starting from ATP. By contrast, the ability of these mutants to form the intermediate starting from phosphate was not impaired. In two mutants (Glu423 and Asp883) it was even enhanced. Two conserved Pro residues of TM4 were also mutated, leading to the loss of the ability of the pump to form the Ca2+- and ATP-dependent phosphorylated intermediate, Unexpectedly, two of the mutations (Asn879 and Gln971) led to the mistargeting of the mutated proteins, i.e., to their retention in the endoplasmic reticulum.
机译：已在COS-7细胞中表达了质膜Ca2 +泵（PMCA）的突变体，其中跨膜结构域（TM）4、6和8中的氨基酸已被替换。通过测量微粒体制剂中Ca2 +的吸收并跟踪由ATP和磷酸盐形成的磷酸化中间体，对它们进行了功能分析。突变的残基对应于其氨基酸在肌浆网泵（SERCA）中的突变导致泵蛋白损失Ca2 +转运的氨基酸：然而，六个SERCA残基中只有四个在PMCA泵中保守。 Glu423（TM4），Asn879或Asp883（TM6）或Gln971（TM8）的突变抑制了泵的Ca2 +转运及其从ATP形成磷酸化中间体的能力。相反，这些突变体从磷酸盐开始形成中间体的能力没有受到损害。在两个突变体（Glu423和Asp883）中，它甚至得到增强。 TM4的两个保守的Pro残基也被突变，导致泵形成Ca2 +和ATP依赖的磷酸化中间体的能力丧失。出乎意料的是，两个突变（Asn879和Gln971）导致突变的错误定位蛋白质，即使其保留在内质网中。

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