Structure and function of MAM22 protein which is localized in magnetosome membranes of Magnetospirillum magnetotacticum

我克隆了编码MAM22的基因，并对其进行了序列分析，该基因定位于磁螺菌的磁小体膜上。氨基酸序列推测为MSSKPSDILD-EVTLYAHYGLSVAKKLGMNMVDAFRAAFSVNDDIRQVYYRDKGISHAKAGRYSQAVMLLEQVYDADAFDVDVALHLGIAYVKTGAVDRGTELLERSLADAPDNVKVATVLGLTYVQVQKYDLAVPLLIKVAEANPINFNVRFRLGVALDNLGRFDEAIDSFKIALACVPMKARCIAPSPSAMSRWAGTRKPCRISRRPMNLTKGPRSEAV(DDBJ登录号：D82942)。用BLAST软件将推导的MAM22氨基酸序列与Gen Bank和Swiss Prot数据库进行比对。它与许多属于TPR蛋白家族的蛋白同源。MAM22的中心有三个排列整齐的TPR单元。在过氧化体蛋白输入受体和线粒体外膜蛋白中已经发现了具有TPR基序的蛋白质，它们被认为是核编码前蛋白的输入受体。在磁小体中发现一种带有TPR基序的蛋白质，将对趋磁细菌合成磁铁矿的机制提供重要的建议。

I cloned and sequenced the gene encoding MAM22 which was localized in magnetosome membranes of Magnetospirillum magnetotacticum. The amino acid sequence was deduced to be MSSKPSDILD-EVTLYAHYGLSVAKKLGMNMVDAFRAAFSVNDDIRQVYYRDKGISHAKAGRYSQAVMLLEQVYDADAFDVDVALHLGIAYVKTGAVDRGTELLERSLADAPDNVKVATVLGLTYVQVQKYDLAVPLLIKVAEANPINFNVRFRLGVALDNLGRFDEAIDSFKIALACVPMKARCIAPSPSAMSRWAGTRKPCRISRRPMNLTKGPRSEAV (DDBJ Accession No.D82942). The deduced amino acid sequence of MAM22 was compared with the Gen Bank and SWISS PROT data base by the BLAST program. It was homologous to a number of proteins that belong to TPR protein family. MAM22 contained three tandemly arranged TPR units in its center. The proteins with TPR motifs have been identified in the peroxisomal protein import receptors and the mitochondrial outer membrane proteins which are thought to function as import receptors for nuclear encoded preproteins. The finding of a protein with TPR motifs in magnetosomes would provide important suggestions concerning the mechanism of magnetite synthesis in magnetotactic bacteria.