Characterization of the third member of the MCAT family of cationic amino acid transporters. Identification of a domain that determines the transport properties of the MCAT proteins.
Characterization of the third member of the MCAT family of cationic amino acid transporters. Identification of a domain that determines the transport properties of the MCAT proteins.
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DOI：
10.1016/s0021-9258(19)36854-1
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发表时间：
1993-10
期刊：
影响因子：
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通讯作者：
E. Closs;C. Richard;Carol Kelly;J. Cunningham
中科院分区：
文献类型：
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作者：
E. Closs;C. Richard;Carol Kelly;J. Cunningham
我们已经在脂多糖刺激的小鼠巨噬细胞中鉴定出阳离子氨基酸转运蛋白家族的第三个成员。该转运蛋白的氨基酸序列与在肝细胞中表达的低亲和力转运蛋白MCAT-2(小鼠阳离子氨基酸转运蛋白-2)相同，除了连接第八和第九跨膜结构域的41个氨基酸外。这些转运蛋白显然是单个基因转录本差异剪接的结果，因此被命名为MCAT-2A(肝细胞)和MCAT-2B(巨噬细胞)。尽管它们相似，MCAT-2B在精氨酸浓度的五分之一时是饱和的，具有较低的表观Vmax，并且比MCAT-2对反式刺激更敏感。将MCAT-2A和MCAT-2B的独特区域引入相关蛋白的等效部分MCAT-1，创建了嵌合转运体，其性质最像该区域的供体。我们的发现表明，这41个氨基酸包含一个结构域，在氨基酸底物跨膜转运过程中与其结合。
We have identified the third member of a family of cationic amino acid transporters in lipopolysaccharide-stimulated murine macrophages. The deduced amino acid sequence of this transporter is the same as MCAT-2 (mouse cationic amino acid transporter-2), the low affinity transporter expressed in hepatocytes, except for a stretch of 41 amino acids that connects the eighth and ninth membrane-spanning domains. These transporters apparently result from differential splicing of transcripts from a single gene and therefore have been named MCAT-2A (hepatocyte) and MCAT-2B (macrophage). Despite their similarity, MCAT-2B is saturated at one-fifth the arginine concentration, has a lower apparent Vmax, and is more sensitive to trans-stimulation than MCAT-2. Introduction of the unique regions of MCAT-2A and MCAT-2B into the equivalent portion of the related protein, MCAT-1, created chimeric transporters with properties most like the donor of this region. Our findings suggest these 41 amino acids contain a domain that binds the amino acid substrate during its translocation across the membrane.