Excitation energy trapping in pho in Lhca1 an

rmga route. We suggest that the specific location of each Lhca protein within the PSI–LHCI supercomplex is more important than the presence of so-called red chlorophylls in the Lhca proteins. a + bmolecules and 12 xanthophylls [1]. The function of LHCI tained from Arabidopsis lines lacking a specific light-harvesting FEBS 29853 FEBS Letters 579 (2005) 4787–4791light-harvesting complex Iis to increase the absorption cross-section of PSI and to deliver excitation energy for the PSI core complex, in which photo-chemical charge separation takes place. Green plant LHCI normally consists of four different proteins Lhca1–4 [2] that each have been shown to be present with one copy per PSI [3]. Another protein (Lhca5) is present in substoichiometric protein of photosystem I (Lhca) protein [5]. Here, we report a detailed analysis by time-resolved fluorescence spectroscopy of the particles obtained from knock-out mutants of the Lhca1 and Lhca4 genes. In the particles from the first mutant, the re-sults provide information on energy transfer characteristics of Lhca2 and Lhca3, whereas in those from the second mutant the results give details on an Lhca protein without red chloro-phylls, most likely Lhca5. 2. Materials and methods PSI–LHCI particles were isolated from Arabidopsis thaliana plant lines depleted in the expression of distinct Lhca protein subtypes as de-scribed in Klimmek et al. [5]. The samples were diluted with a buffe