Inukai M, Ghrayeb J, Nakamura K, Inouye M
J Biol Chem. 1984 Jan 25;259(2):757-60.
A new intermediate (apolipoprotein) in the synthesis of the major lipoprotein of the Escherichia coli outer membrane has been identified. The accumulation of this new form of the lipoprotein was observed when excessive production of lipoprotein was induced or when the membrane fraction containing the prolipoprotein accumulated in the presence of globomycin was incubated at 60 degrees C. The new form of the lipoprotein could be chased into the mature lipoprotein. In addition, from sequential analysis of this new protein by Edman degradation, the NH2 terminus was found to be cysteine, containing a free unmodified amino group and a glyceride-modified sulfhydryl group. These results indicate that this protein is an intermediate in the conversion of glyceride-modified prolipoprotein to the mature lipoprotein. It is believed that the lipoprotein signal peptidase directly cleaves the lipoprotein signal peptide at the peptide bond between the glycine residue at position 20 and the cysteine residue at position 21 of the prolipoprotein. The resulting intermediate, designated here as apolipoprotein, is subsequently acylated at its free amino group to yield the final mature lipoprotein.
已鉴定出大肠杆菌外膜主要脂蛋白合成过程中的一种新中间体（载脂蛋白）。当诱导脂蛋白过量产生时，或者当含有前脂蛋白的膜部分在球霉素存在下积累并于60℃孵育时，可观察到这种新形式脂蛋白的积累。这种新形式的脂蛋白可被追踪转化为成熟脂蛋白。此外，通过埃德曼降解对这种新蛋白质进行序列分析，发现其NH2末端为半胱氨酸，含有一个游离的未修饰氨基和一个甘油酯修饰的巯基。这些结果表明，该蛋白质是甘油酯修饰的前脂蛋白转化为成熟脂蛋白过程中的中间体。据信，脂蛋白信号肽酶直接在前脂蛋白第20位甘氨酸残基和第21位半胱氨酸残基之间的肽键处切割脂蛋白信号肽。由此产生的中间体，在此称为载脂蛋白，随后在其游离氨基处被酰化，产生最终的成熟脂蛋白。
