Molecular mechanism of processing of precursor proteins in organelles derived from parasitic organisms

寄生生物细胞器中前体蛋白的加工机制。(1)线粒体加工肽酶：利用基于前体延伸肽氨基酸序列的各种合成肽进行系统和定量分析，证明切割位点周围的残基，包括近端的精氨酸和1、2、3位的残基，以及远端的碱性氨基酸似乎负责识别底物和确定β的切割位点。通过定点突变实验确定了MPP中的功能性氨基酸残基。缩短α-mPP中的富含甘氨酸的部分导致酶与底物多肽的相互作用和切割反应显著减少。荧光共振能量转移(FRET)测量表明，延伸肽的N端部分和裂解位点附近的部分与MPP分子中的特定位点相互作用。利用X射线结晶学技术对重组酵母MPP及其与合成信号肽结合的裂解缺陷突变体MPP的结构进行了测定。(2)原生动物MPP样蛋白酶：获得了锥虫MPP样蛋白酶的基因片段，并推导了其氨基酸序列。

Mechanism of processing of precursor proteins in organelles derived from parasitic organisms.(1) Mitochondrial processing peptidase : Systematic and quantitative analyses, using various synthetic peptides based on the amino acid sequence of the extension peptides of the precursors, demonstrated that a combination of residues around the cleavage site, including the proximal arginine and residues at positions 1, 2, and 3, and the distal basic amino acids appears to be responsible for recognition of the substrates and for determination of the cleavage site by MPP.Functional amino acid residues in β-MPP were determined by site-directed mutation experiments. Shortening of the glycine-rich stretch in α-MPP led to a dramatic reduction of interaction between the enzyme and substrate peptides and cleavage reaction. Fluorescence resonance energy transfer (FRET) measurements indicate that the N-terminal portion and the portion around the cleavage site of the extension peptides interact with specific sites in the MPP molecule. The structures of recombinant yeast MPP and a cleavage-deficient mutant of MPP complexed with synthetic signal peptides were determined using X-ray crystallographic techniques.(2) MPP-like proteases of protozoan : cDNAs of MPP-like proteases of trypanosoma was obtained and the amino acid sequence was deduced.