Vainstein A, Peterson C C, Thornber J P
Department of Biology, University of California, Los Angeles 90024.
J Biol Chem. 1989 Mar 5;264(7):4058-63.
Three different pigment-binding proteins of the light-harvesting complex (LHC I) of maize photosystem I (PS I) have been isolated. Absorption and fluorescence excitation spectral analyses showed that each pigment-protein can transfer absorbed energy from its carotenoid and/or chlorophyll b components to chlorophyll alpha. Their apoproteins with apparent sizes of 24 (LHC Ia), 21 (LHC Ib), and 17 (LHC Ic) kDa have been purified to homogeneity. Differences in their pigment and amino acid compositions and in their reactions with antibodies demonstrate that the two smaller pigment-proteins are not proteolytically derived from the largest one. LHC Ib's apoprotein is particularly enriched in cysteine residues. None of the three apoproteins cross-reacted with antibodies raised against the major light-harvesting chlorophyll a/b-protein of photosystem II (LHC IIb) or against the PS I core complex (CC I) subunits. Studies of the biogenesis of PS I during greening of etiolated plants showed that all of the CC I subunits accumulated to a detectable level prior to the appearance of the 17-kDa subunit of LHC I, the accumulation of which preceded those of the 24- and 21-kDa subunits of LHC I. In addition, subunit VI of CC I is shown to be differentially expressed in mesophyll and bundle sheath cells; a slightly larger form of it accumulates in mesophyll than in bundle sheath thylakoids during plastid development.
玉米光系统I（PS I）捕光复合体（LHC I）的三种不同色素结合蛋白已被分离出来。吸收光谱和荧光激发光谱分析表明，每种色素蛋白都能将吸收的能量从其类胡萝卜素和/或叶绿素b成分传递给叶绿素a。它们的脱辅基蛋白表观大小分别为24 kDa（LHC Ia）、21 kDa（LHC Ib）和17 kDa（LHC Ic），已纯化至同质。它们在色素和氨基酸组成以及与抗体反应方面的差异表明，两种较小的色素蛋白并非由最大的一种蛋白经蛋白水解衍生而来。LHC Ib的脱辅基蛋白特别富含半胱氨酸残基。这三种脱辅基蛋白均未与针对光系统II主要捕光叶绿素a/b蛋白（LHC IIb）或PS I核心复合体（CC I）亚基产生的抗体发生交叉反应。对黄化植物变绿过程中PS I生物合成的研究表明，所有CC I亚基均在LHC I的17 kDa亚基出现之前积累到可检测水平，而LHC I的17 kDa亚基的积累先于LHC I的24 kDa和21 kDa亚基。此外，CC I的亚基VI在叶肉细胞和维管束鞘细胞中差异表达；在质体发育过程中，其稍大的形式在叶肉中比在维管束鞘类囊体中积累得更多。
