Abstract
Chromophore absorption and emission characteristics of the αAP-B, β18 and Lcm (large core-membrane linker) chromopeptides within the phycobilisome core are investigated using genetically engineered strains of Synechococcus sp. PCC 7002. Steady-state and time-resolved emission were used to examine energy transfer in subcore preparations from the wild-type organism and two mutants. Low-temperature (77 K) emission spectra were also measured for intact phycobilisomes from the wild-type and five mutant strains. Mutants retaining either the αAP-B subunit or the unaltered Lcm chromophore resulted in only small changes in the low-temperature emission spectra, while retention of only the β18 subunit resulted in blue-shifted emission spectra. The Lcm chromophore has a room-temperature absorption maximum at 675 nm. In phycobilisomes at 77 K the αAP-B and Lcm chromophores emit at 682-683 nm, and they are the best candidates for long-wavelength emitters also at room temperature. Overlap of these emission spectra with the absorption of chlorophyll a in the associated thylakoid membrane plays a significant role in excitation transfer from the antenna complexes in cyanobacteria.
Original language | English |
---|---|
Pages (from-to) | 153-162 |
Number of pages | 10 |
Journal | BBA - Bioenergetics |
Volume | 1186 |
Issue number | 3 |
DOIs | |
State | Published - 29 Jul 1994 |
Keywords
- Cyanobacterium
- Energy transfer
- Fluorescence relaxation
- Phycobilisome
- Subcore particle, 18 S