Ali A, Salter-Cid L, Flajnik M F, Heikkila J J
Department of Biology, University of Waterloo, Ontario, Canada.
Comp Biochem Physiol B Biochem Mol Biol. 1996 Apr;113(4):681-7. doi: 10.1016/0305-0491(95)02081-0.
We isolated a full-length cDNA clone encoding a Xenopus laevis 70-kDa heat shock cognate protein, hsc70.I. The protein coding region exhibits a high degree of identity with a number of mammalian hsc70 proteins, such as rat hsc71 (92%), whereas the identity to Xenopus hsp70 is only 80%. These data suggest that the inducible and constitutive forms of hsp70 diverged long before the emergence of amphibians. The Xenopus hsc70.I contains a number of conserved elements, including the ATP-binding domain, a nuclear localization signal and the carboxy-terminal EEVD motif, which has been implicated in several activities associated with chaperonin function. Northern blot analyses revealed that maternal hsc70.I mRNA is present in cleavage and early blastula stages of Xenopus development. After the onset of zygotic transcription at the midblastula stage, the levels of hsc70.I message increase through to the tadpole stages. Furthermore, in contrast to hsp70 mRNA, the relative levels of hsc70.I mRNA are not enhanced after heat shock in embryos and in the kidney epithelial cell line, A6. The levels of hsc70.I mRNA are high in adult spleen and testis, with moderate levels in eye, heart, liver and brain and comparatively low levels in hindlimb muscle.
我们分离出了一个编码非洲爪蟾70 kDa热休克同源蛋白hsc70.I的全长cDNA克隆。该蛋白编码区与多种哺乳动物hsc70蛋白具有高度同源性，如大鼠hsc71（92%），而与非洲爪蟾hsp70的同源性仅为80%。这些数据表明，hsp70的诱导型和组成型在两栖动物出现之前很久就已经分化。非洲爪蟾hsc70.I包含许多保守元件，包括ATP结合结构域、核定位信号和羧基末端EEVD基序，该基序与伴侣蛋白功能相关的多种活性有关。Northern印迹分析显示，母体hsc70.I mRNA存在于非洲爪蟾发育的卵裂期和早期囊胚期。在囊胚中期合子转录开始后，hsc70.I信息的水平一直增加到蝌蚪期。此外，与hsp70 mRNA不同，胚胎和肾上皮细胞系A6在热休克后hsc70.I mRNA的相对水平没有提高。hsc70.I mRNA在成年脾脏和睾丸中水平较高，在眼睛、心脏、肝脏和大脑中水平中等，在后肢肌肉中水平相对较低。
