Dual Targeting of a Processing Peptidase into Both Endosymbiotic Organelles Mediated by a Transport Signal of Unusual Architecture  

作　　者：Bianca Baudisch Ralf Bernd Klosgen 

机构地区：[1]Institute of Biology-Plant Physiology, Martin Luther University Halle-Wittenberg, Weinbergweg 10, 06120 Halle/Saale, Germany

出　　处：《Molecular Plant》2012年第2期494-503,共10页分子植物（英文版）

摘　　要：As a result of the endosymbiotic gene transfer, the majority of proteins of mitochondria and chloroplasts are encoded in the nucleus and synthesized in the cytosol as precursor proteins carrying N-terminal transport signals for the ＇re-import＇ into the respective target organelle. Most of these transport signals are monospecific, although some of them have dual targeting properties, that is, they are recognized both by mitochondria and by chloroplasts as target organelles. We have identified alpha-MPP2, one of the two isoforms of the substrate binding subunit of mitochondrial processing peptidase of Arabidopsis thaliana, as a novel member of this class of nuclear-encoded organelle proteins. As demonstrated by in organello transport experiments with isolated organelles and by in vivo localization studies employing fluorescent chimeric reporter proteins, the N-terminal region of the alpha-MPP2 precursor comprises transport signals for the import into mitochondria as well as into chloroplasts. Both signals are found within the N-terminal 79 residues of the precursor protein, where they occupy partly separated and partly overlapping regions. Deletion mapping combined with in organello and in vivo protein transport studies demonstrate an unusual architecture of this transport signal, suggesting a composition of three functionally separated domains.As a result of the endosymbiotic gene transfer, the majority of proteins of mitochondria and chloroplasts are encoded in the nucleus and synthesized in the cytosol as precursor proteins carrying N-terminal transport signals for the ＇re-import＇ into the respective target organelle. Most of these transport signals are monospecific, although some of them have dual targeting properties, that is, they are recognized both by mitochondria and by chloroplasts as target organelles. We have identified alpha-MPP2, one of the two isoforms of the substrate binding subunit of mitochondrial processing peptidase of Arabidopsis thaliana, as a novel member of this class of nuclear-encoded organelle proteins. As demonstrated by in organello transport experiments with isolated organelles and by in vivo localization studies employing fluorescent chimeric reporter proteins, the N-terminal region of the alpha-MPP2 precursor comprises transport signals for the import into mitochondria as well as into chloroplasts. Both signals are found within the N-terminal 79 residues of the precursor protein, where they occupy partly separated and partly overlapping regions. Deletion mapping combined with in organello and in vivo protein transport studies demonstrate an unusual architecture of this transport signal, suggesting a composition of three functionally separated domains.

关 键 词：Protein transport dual targeting MITOCHONDRIA CHLOROPLASTS mitochondrial processing peptidase 

分 类 号：Q244[生物学—细胞生物学] U491.51[交通运输工程—交通运输规划与管理]