Okamoto T, Ohkuni Y, Ogata E, Nishimoto I
Fourth Department of Internal Medicine, University of Tokyo School of Medicine, Japan.
Biochem Biophys Res Commun. 1991 Aug 30;179(1):10-6. doi: 10.1016/0006-291x(91)91326-8.
Arg2410-Lys2423 (RVGLVRGEKARKGK, peptide 14) of the human insulin-like growth factor II receptor directly activates Gi and deletion of C-terminal 4 residues from peptide 14 nullifies this activity. A study was thus made of the effects of peptides modified in the C-terminal structure. RVGLVRGEKAAKGK and RVGLVRGEKARKGA scarcely activated Gi, whereas RVGLVRGEKARAGK (peptide A5) activated Gi as much as peptide 14 did. However, peptide A5 action did not depend on Mg2+ concentration and was little affected by pertussis toxin modification of Gi alpha. Peptide A5 may thus recognize the region on Gi alpha that is distinct from the extreme C-terminus. It is consequently considered that (i) the first and the last basic residues in the C-terminal motif of peptide 14 determine the capacity for recognition of Gi and (ii) there is a region different from the C-terminus of Gi alpha, through which the C-terminal second basic residue-altered peptide 14 activates Gi in a Mg(2+)-independent manner.
人胰岛素样生长因子II受体的Arg2410-Lys2423（RVGLVRGEKARKGK，肽14）直接激活Gi，从肽14的C末端缺失4个残基会使该活性丧失。因此，开展了一项关于C末端结构修饰肽的作用的研究。RVGLVRGEKAAKGK和RVGLVRGEKARKGA几乎不激活Gi，而RVGLVRGEKARAGK（肽A5）激活Gi的程度与肽14相同。然而，肽A5的作用不依赖于Mg2+浓度，并且几乎不受Giα的百日咳毒素修饰的影响。因此，肽A5可能识别Giα上与极端C末端不同的区域。因此可以认为：（i）肽14的C末端基序中的第一个和最后一个碱性残基决定了识别Gi的能力；（ii）存在一个与Giα的C末端不同的区域，通过该区域，C末端第二个碱性残基改变的肽14以Mg(2+)非依赖性方式激活Gi。
