Thylakoid membranes are potentially a wonderful model biological membrane system. Not only is there outstanding structural information on many of the thylakoid membrane protein complexes, but also a battery of functional assays of light-harvesting and electron transport that make it very easy to probe membrane function in detail. However, there is one area where there is a distinct gap in current knowledge of thylakoid membrane function. There is very little direct information about the dynamics of thylakoid membranes. Diffusion of membrane components has been invoked in a number of contexts, for example, to explain electron transport (Kirchhoff et al., 2002), adaptation of the light-harvesting apparatus (Allen and Forsberg, 2001), and the biogenesis, turnover, and repair of the photosystems (Baena-Gonzalez et al., 1999). Diffusion coefficients for certain thylakoid membrane components have been estimated by indirect means (Drepper et al., 1993; Blackwell et al., 1994), but current knowledge of thylakoid membrane dynamics remains very fragmentary. For example, it is not clear whether the major membrane protein complexes are locked into a semi-crystalline array, or whether they are freely mobile and interact transiently by collision, as is more normal in biological systems (Storrie and Kreis, 1996). In the absence of this basic information, detailed models cannot be built for many aspects of thylakoid membrane function, from electron transport to the turnover and repair of Photosystem II.
Answers to all your Biology Questions
