GENETICALLY MODIFIED PHOTOSYNTHETIC ANTENNA COMPLEXES WITH BLUESHIFTED ABSORBENCY BANDS

被引:234
作者
FOWLER, GJS [1 ]
VISSCHERS, RW [1 ]
GRIEF, GG [1 ]
VANGRONDELLE, R [1 ]
HUNTER, CN [1 ]
机构
[1] FREE UNIV AMSTERDAM,DEPT PHYS & ASTRON,1081 HV AMSTERDAM,NETHERLANDS
关键词
D O I
10.1038/355848a0
中图分类号
O [数理科学和化学]; P [天文学、地球科学]; Q [生物科学]; N [自然科学总论];
学科分类号
07 ; 0710 ; 09 ;
摘要
LIGHT energy for photosynthesis is collected by the antenna system, creating an excited state which migrates energetically 'downhill'. To achieve efficient migration of energy the antenna is populated with a series of pigments absorbing at progressively redshifted wavelengths. This variety in absorbing species in vivo has been created in a biosynthetically economical fashion by modulating the absorbance behaviour of one kind of (bacterio) chlorophyll molecule. This modulation is poorly understood but has been ascribed to pigment-pigment and pigment-protein interactions. We have examined the relationship between aromatic residues in antenna polypeptides and pigment absorption, by studying the effects of site-directed mutagenesis on a bacterial antenna complex. A clear correlation was observed between the absorbance of bacteriochlorophyll a and the presence of two tyrosine residues, alpha-Tyr44 and alpha-Tyr45, in the alpha-subunit of the peripheral light-harvesting complex of Rhodobacter sphaeroides, a purple photosynthetic bacterium that provides a well characterized system for site-specific mutagenesis 1-3. By constructing single (alpha-Tyr44, alpha-Tyr45 --> PheTyr) and then double (alpha-Tyr44, alpha-Tyr45 --> PheLeu) site-specific mutants, the absorbance of bacteriochlorophyll was blueshifted by 11 and 24 nm at 77 K, respectively. The results suggest that there is a close approach of tyrosine residues to bacteriochlorophyll, and that this proximity may promote redshifts in vivo.
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页码:848 / 850
页数:3
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