Li Hui, Bryant Donald A
Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802, USA.
J Bacteriol. 2009 Nov;191(22):7109-20. doi: 10.1128/JB.00707-09. Epub 2009 Sep 11.
The chlorosome envelope of Chlorobaculum tepidum contains 10 proteins that belong to four structural motif families. A previous mutational study (N.-U. Frigaard, H. Li, K. J. Milks, and D. A. Bryant, J. Bacteriol. 186:646-653, 2004) suggested that some of these proteins might have redundant functions. Six multilocus mutants were constructed to test the effects of eliminating the proteins of the CsmC/CsmD and CsmB/CsmF motif families, and the resulting strains were characterized physiologically and biochemically. Mutants lacking all proteins of either motif family still assembled functional chlorosomes, and as measured by growth rates of the mutant strains, light harvesting was affected only at the lowest light intensities tested (9 and 32 micromol photons m(-2) s(-1)). The size, composition, and biogenesis of the mutant chlorosomes differed from those of wild-type chlorosomes. Mutants lacking proteins of the CsmC/CsmD motif family produced smaller chlorosomes than did the wild type, and the Q(y) absorbance maximum for the bacteriochlorophyll c aggregates in these chlorosomes was strongly blueshifted. Conversely, the chlorosomes of mutants lacking proteins of the CsmB/CsmF motif family were larger than wild-type chlorosomes, and the Q(y) absorption for their bacteriochlorophyll c aggregates was redshifted. When CsmH was eliminated in addition to other proteins of either motif family, chlorosomes had smaller diameters. These data show that the chlorosome envelope proteins of the CsmB/CsmF and CsmC/CsmD families play important roles in determining chlorosome size as well as the assembly and supramolecular organization of the bacteriochlorophyll c aggregates within the chlorosome.
嗜温绿菌（Chlorobaculum tepidum）的叶绿体包膜含有10种蛋白质，这些蛋白质属于四个结构基序家族。先前的一项突变研究（N.-U.弗里加德、H.李、K.J.米尔克斯和D.A.布赖恩特，《细菌学杂志》186:646 - 653，2004年）表明，其中一些蛋白质可能具有冗余功能。构建了六个多位点突变体，以测试消除CsmC/CsmD和CsmB/CsmF基序家族蛋白质的影响，并对所得菌株进行生理和生化特征分析。缺乏任何一个基序家族所有蛋白质的突变体仍能组装功能性叶绿体，并且通过突变菌株的生长速率测量发现，仅在测试的最低光照强度（9和32微摩尔光子·米⁻²·秒⁻¹）下，光捕获受到影响。突变叶绿体的大小、组成和生物发生与野生型叶绿体不同。缺乏CsmC/CsmD基序家族蛋白质的突变体产生的叶绿体比野生型小，并且这些叶绿体中细菌叶绿素c聚集体的Q(y)吸收最大值发生强烈蓝移。相反，缺乏CsmB/CsmF基序家族蛋白质的突变体的叶绿体比野生型大，并且其细菌叶绿素c聚集体的Q(y)吸收发生红移。当除了任何一个基序家族的其他蛋白质之外还消除CsmH时，叶绿体的直径更小。这些数据表明，CsmB/CsmF和CsmC/CsmD家族的叶绿体包膜蛋白在确定叶绿体大小以及叶绿体内细菌叶绿素c聚集体的组装和超分子组织方面发挥着重要作用。
