Adolph Kenneth W
Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, 6-155 Jackson Hall, 321 Church Street SE, Minneapolis, MN, 55455, USA.
DNA Seq. 2005 Aug;16(4):252-9. doi: 10.1080/10425170500129660.
The cDNA and protein structures of Xenopus metaxin 3, along with those of Xenopus metaxins 1 and 2, have been characterized. A protein of 309 amino acid residues is encoded by X. laevis metaxin 3 (XMTX3) cDNA. In comparison, the cDNA of X. laevis metaxin 1 (XMTX1) specifies a protein of 320 residues, while the metaxin 2 cDNAs of X. laevis (XMTX2) and X. tropicalis (SMTX2) both specify proteins of 274 amino acids. Aligning the amino acid sequences of XMTX3 and XMTX1 showed 39% identities; 22% identities were found for XMTX3 and XMTX2. However, 55% amino acid identities were revealed in aligning the XMTX3 and zebrafish metaxin 3 sequences. The construction of a phylogenetic tree gave further evidence for the existence of three distinct groups of metaxin genes and their common ancestry. Two conserved protein domains are present in each of the Xenopus metaxins: a glutathione S-transferase (GST) domain and a thioredoxin-like domain. The protein secondary structure predicted for the Xenopus metaxins is dominated by regions of alpha helix which alternate with regions that are neither alpha helix nor beta strand.
非洲爪蟾间变蛋白3以及非洲爪蟾间变蛋白1和2的cDNA和蛋白质结构已得到表征。非洲爪蟾间变蛋白3（XMTX3）cDNA编码一个由309个氨基酸残基组成的蛋白质。相比之下，非洲爪蟾间变蛋白1（XMTX1）的cDNA编码一个由320个残基组成的蛋白质，而非洲爪蟾（XMTX2）和热带爪蟾（SMTX2）的间变蛋白2 cDNA均编码由274个氨基酸组成的蛋白质。XMTX3和XMTX1的氨基酸序列比对显示有39%的一致性；XMTX3和XMTX2的一致性为22%。然而，XMTX3与斑马鱼间变蛋白3序列比对显示有55%的氨基酸一致性。系统发育树的构建进一步证明了存在三组不同的间变蛋白基因及其共同祖先。非洲爪蟾的每种间变蛋白都有两个保守的蛋白质结构域：一个谷胱甘肽S-转移酶（GST）结构域和一个硫氧还蛋白样结构域。预测的非洲爪蟾间变蛋白的蛋白质二级结构主要由α螺旋区域组成，这些区域与既不是α螺旋也不是β链的区域交替出现。
