Supramolecular Photosystem II Organization in Grana Thylakoid Membranes: Evidence for a Structured Arrangement

详细信息    查看全文

• 作者：Helmut Kirchhoff ; Ira Tremmel ; Winfried Haase ; and Ulrich Kubitscheck
• 刊名：Biochemistry
• 出版年：2004
• 出版时间：July 20, 2004
• 年：2004
• 卷：43
• 期：28
• 页码：9204 - 9213
• 全文大小：211K
• 年卷期：v.43,no.28(July 20, 2004)
• ISSN：1520-4995

文摘

The distribution of photosystem (PS) II complexes in stacked grana thylakoids derived fromelectron microscopic images of freeze-fractured chloroplasts are examined for the first time usingmathematical methods. These characterize the particle distribution in terms of a nearest neighbor distributionfunction and a pair correlation function. The data were compared with purely random distributions calculatedby a Monte Carlo simulation. The analysis reveals that the PSII distribution in grana thylakoids does notcorrespond to a random protein mixture but that ordering forces lead to a structured arrangement on asupramolecular level. Neighboring photosystems are significantly more separated than would be the casein a purely random distribution. These results are explained by structural models, in which boundarylipids and light-harvesting complex (LHC) II trimers are arranged between neighboring PSII. Furthermore,the diffusion of PSII was analyzed by a Monte Carlo simulation with a protein density of 80% areaoccupation (determined for grana membranes). The mobility of the photosystems is severely reduced bythe high protein density. From an estimate of the mean migration time of PSII from grana thylakoids tostroma lamellae, it becomes evident that this diffusion contributes significantly to the velocity of therepair cycle of photoinhibited PSII.