m, a Structural Member of the X,K-ATPase bs.acs.org/images/gifchars/beta2.gif" border="0" align="m

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• 作者：Gilles Crambert ; Pascal Bé ; guin ; Nikolay B. Pestov ; Nikolai N. Modyanov ; and K&auml ; thi Geering
• 刊名：Biochemistry
• 出版年：2002
• 出版时间：May 28, 2002
• 年：2002
• 卷：41
• 期：21
• 页码：6723 - 6733
• 全文大小：200K
• 年卷期：v.41,no.21(May 28, 2002)
• ISSN：1520-4995

文摘

beta2.gif" BORDER=0 ALIGN="middle">m, a muscle-specific protein, is structurally closely related to the X,K-ATPase beta2.gif" BORDER=0 ALIGN="middle"> subunits,but its intrinsic function is not known. In this study, we have expressed beta2.gif" BORDER=0 ALIGN="middle">m in Xenopus oocytes and haveinvestigated its biosynthesis and processing as well as its putative role as a chaperone of X,K-ATPase subunits, as a regulator of sarcoplasmic reticulum Ca²⁺-ATPase (SERCA), or as a Ca²⁺-sensing protein.Our results show that beta2.gif" BORDER=0 ALIGN="middle">m is stably expressed in the endoplasmic reticulum (ER) in its core glycosylated,partially trimmed form. Both full-length beta2.gif" BORDER=0 ALIGN="middle">m, initiated at Met¹, and short beta2.gif" BORDER=0 ALIGN="middle">m species, initiated at Met⁸⁹,are detected in in vitro translations as well as in Xenopus oocytes. beta2.gif" BORDER=0 ALIGN="middle">m cannot associate with and stabilizeNa,K-ATPase (NK), or gastric and nongastric H,K-ATPase (HK) isoforms. beta2.gif" BORDER=0 ALIGN="middle">m neither assembles stablywith SERCA nor is its trypsin sensitivity or electrophoretic mobility influenced by Ca²⁺. A mutant, inwhich the distinctive Glu-rich regions in the beta2.gif" BORDER=0 ALIGN="middle">m N-terminus are deleted, remains stably expressed in theER and can associate with, but not stabilize X,K-ATPase subunits. On the other hand, a chimera inwhich the ectodomain of beta2.gif" BORDER=0 ALIGN="middle">m is replaced with that of beta2.gif" BORDER=0 ALIGN="middle">1 NK associates efficiently with NK isoformsand produces functional Na,K-pumps at the plasma membrane. In conclusion, our results indicate thatbeta2.gif" BORDER=0 ALIGN="middle">m exhibits a cellular location and functional role clearly distinct from the typical X,K-ATPase beta2.gif" BORDER=0 ALIGN="middle"> subunits.