Structure and function of stress proteins

通过反义转染实验研究HSP 47的功能。发现表达HSP 47的反义RNA的稳定转染子也合成减少量的I型胶原。将编码α 1（I）胶原基因的cDNA转染这些细胞株后，在洗涤剂不溶性组分中回收了过表达的胶原，提示HSP 47的分子伴侣功能维持了胶原的新生多肽在内质网中的可溶性。测定了GroEL与α-LA在还原态和moleten小球态相互作用的解离常数、离子强度效应和速率常数。MSF依赖性途径，其中新生蛋白质通过MSF的功能靶向膜受体，在高尔基体膜上发现了一种新的膜蛋白Rer 1 p。Rer 1 p被认为参与了质量控制机制，因为错误地运输到高尔基体的蛋白质通过该蛋白质的功能返回内质网。

Experiment of antisense transfection was performed to elucidate the function of HSP47, a collagen-specific molecular chaperone. Stable transfectant expressing the antisense RNA of HSP47 were found to synthesize reduced amounts of type I collagen as well. When cDNA encoding alpha1 (I) collagen gene was transfected into these cell lines, overexpressed collagen was recovered in the detergent-insoluble fraction, suggesting the chaperone function of HSP47 which maintain the nascent polypeptide of collagen to be soluble in the endoplasmic reticulum.Molecular mechanism on the recognition of target proteins by GroEL was analyzed using alpha-lactalbumin (alpha-LA). Dissociation constants, effect of ioninc strength and rate constants of the interaction of GroEL with alpha-LA in the reduced state as well as in the moleten globule state were determined.Two independent pathways of the transports of nascent proteins into mitochondria were established : MSF-dependent pathway where nascent proteins are targeted to membrane receptors via the function of MSF,and MSF-independent pathway where proteins are directly handled to Mas20/Mass22 receptor on the mitochondrial membrane.A novel membrane protein, Rer1p, was found in the golgi membrane. Rer1p was suggested to be involved in the quality control mechanism since the incorrectly transported proteins to the Golgi are returned back to the endoplasimic reticulum by the function of this protein.