Panter S, Thomson R, de Bruxelles G, Laver D, Trevaskis B, Udvardi M
Department of Biochemistry and Molecular Biology, Australian National University, Canberra ACT, Australia.
Mol Plant Microbe Interact. 2000 Mar;13(3):325-33. doi: 10.1094/MPMI.2000.13.3.325.
Soybean peribacteroid membrane (PBM) proteins were isolated from nitrogen-fixing root nodules and subjected to N-terminal sequencing. Sequence data from 17 putative PBM proteins were obtained. Six of these proteins are homologous to proteins of known function. These include three chaperones (HSP60, BiP [HSP70], and PDI) and two proteases (a serine and a thiol protease), all of which are involved in some aspect of protein processing in plants. The PBM homologs of these proteins may play roles in protein translocation, folding, maturation, or degradation in symbiosomes. Two proteins are homologous to known, nodule-specific proteins from soybean, nodulin 53b and nodulin 26B. Although the function of these nodulins is unknown, nodulin 53b has independently been shown to be associated with the PBM. All of the eight proteins with identifiable homologs are likely to be peripheral rather than integral membrane proteins. Possible reasons for this apparent bias are discussed. The identification of homologs of HSP70 and HSP60 associated with the PBM is the first evidence that the molecular machinery for co- or post-translational import of cytoplasmic proteins is present in symbiosomes. This has important implications for the biogenesis of this unique, nitrogen-fixing organelle.
从固氮根瘤中分离出大豆类周膜（PBM）蛋白，并对其进行N端测序。获得了17种假定的PBM蛋白的序列数据。其中六种蛋白与已知功能的蛋白同源。这些蛋白包括三种伴侣蛋白（热休克蛋白60、结合免疫球蛋白蛋白[热休克蛋白70]和蛋白二硫键异构酶）和两种蛋白酶（一种丝氨酸蛋白酶和一种硫醇蛋白酶），它们都参与植物蛋白质加工的某些方面。这些蛋白的PBM同源物可能在共生体中的蛋白质转运、折叠、成熟或降解中发挥作用。两种蛋白与大豆已知的结节特异性蛋白结节球蛋白53b和结节球蛋白26B同源。尽管这些结节球蛋白的功能尚不清楚，但已独立证明结节球蛋白53b与PBM有关。所有八种具有可识别同源物的蛋白可能都是外周蛋白而非整合膜蛋白。文中讨论了这种明显偏差的可能原因。与PBM相关的热休克蛋白70和热休克蛋白60同源物的鉴定是共生体中存在细胞质蛋白共翻译或翻译后导入分子机制的首个证据。这对这个独特的固氮细胞器的生物发生具有重要意义。
