Systematic discovery of N-end-rule substrate proteins

i）当不稳定蛋白质在细胞内积累时，缺陷蛋白质降解系统（即泛素连接酶）的突变酵母菌株存活。此时，细胞过表达Obr 1蛋白以克服应激条件。ii）系统地进行具有不同N-末端倒数第二个残基的N-末端规则底物肽的L/F-转移酶的动力学分析。该分析表明残基的侧链影响对转移酶的底物结合亲和力。它提供了生物学洞察的倒数第二个氨基酸对底物特异性的天然蛋白质降解通过N-末端规则途径的影响。

i) A mutant yeast strain that defects protein degradation system (i.e. ubiquitin ligase) survives when a destabilizing protein is accumulated inside the cell. At that time, the cell overexpresses Obr1 protein to overcome the stressed condition. ii) Kinetic analysis of L/F-transferase with N-end-rule substrate peptides posessing different N-terminal penultimate residues is systematically performed. This analysis suggests that the side chain of the residue affects substrate-binding afffinity towards the transferase. It gives biological insight into the effect of the penultimate amino acid on substrate specificity of natural proteins to be degraded via the N-end rule pathway.