Alexander N. Glazer
University of California, Berkeley
Election Year: 2001
Primary Section: 21, Biochemistry
Secondary Section: 63, Environmental Sciences and Ecology
Membership Type: Member
My laboratory explores the structure and function of large photosynthetic light-harvesting complexes called phycobilisomes. A general feature of such complexes is the presence of numerous "antenna pigments" that absorb light and transfer the excitation energy from pigment to pigment by radiationless energy transfer processes with an overall efficiency greater than 95 percent to a special chlorophyll or bacteriochlorophyll in the reaction center for subsequent conversion to electron flow. Phycobilisomes are the principal light harvesters in cyanobacteria and red algae. These intricate complexes, of 6 to 8 million daltons, are made up entirely of proteins, with 500 to 700 covalently attached linear tetrapyrroles (bilins) that absorb visible light over a wide spectral range. Phycobilisomes are the largest light-harvesting complexes known that can be isolated in intact form. Our work showed that the differences in the absorbance properties of the individual bilins and the details of their spatial arrangement in the phycobilisome lead to a highly directional pathway for energy transfer toward the reaction center irrespective of where in the phycobilisome the photon is absorbed. With respect to the rate-determining steps in energy transfer, phycobilisomes function as if they were arrays of no more than a half-dozen pigment molecules.