McCourt P, Browse J, Watson J, Arntzen C J, Somerville C R
MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, Michigan 48824.
Plant Physiol. 1985 Aug;78(4):853-8. doi: 10.1104/pp.78.4.853.
Several lines of evidence support the proposal that the unusual chloroplast-specific lipid acyl group Delta3,trans-hexadecenoic acid (trans-C(16:1)) stimulates the formation or maintenance of the oligomeric form of the light-harvesting chlorophyll a/b complex (LHCP). To assess the functional significance of this apparent association we have analyzed LHCP structure and function in a mutant of Arabidopsis thaliana (L.) which lacks trans-C(16:1) by electrophoretic analysis of the protein-chlorophyll complexes and by measurements of chlorophyll fluorescence under a variety of conditions. By these criteria the putative oligomeric form of LHCP appears to be slightly more labile to detergent-mediated dissociation in the mutant. The oligomeric PSI chlorophyll-protein complex, associated with PSI, was also more labile to detergent-mediated dissociation in the mutant, suggesting a previously unsuspected association of trans-C(16:1) with the PSI complex. However, no significant effect of the mutation on the efficiency of energy transfer from LHCP to the photochemical reaction centers was observed under any of the various conditions imposed. Also, the stability of the chlorophyll-protein complexes to temperature-induced dissociation was unaffected in the mutant. The role of trans-C(16:1) is very subtle or is only conditionally expressed.
叶绿体特有的异常脂质酰基——Δ3，反式十六碳烯酸（反式C(16:1)）能刺激捕光叶绿素a/b复合物（LHCP）寡聚体形式的形成或维持。为了评估这种明显关联的功能意义，我们通过对蛋白质 - 叶绿素复合物进行电泳分析以及在多种条件下测量叶绿素荧光，分析了拟南芥（L.）一个缺乏反式C(16:1)的突变体中LHCP的结构和功能。基于这些标准，LHCP的假定寡聚体形式在突变体中似乎对去污剂介导的解离稍微更不稳定。与光系统I（PSI）相关的寡聚PSI叶绿素 - 蛋白质复合物在突变体中对去污剂介导的解离也更不稳定，这表明反式C(16:1)与PSI复合物存在之前未被怀疑的关联。然而，在施加的任何各种条件下，均未观察到该突变对能量从LHCP转移到光化学反应中心的效率有显著影响。此外，叶绿素 - 蛋白质复合物对温度诱导解离的稳定性在突变体中未受影响。反式C(16:1)的作用非常微妙，或者只是在特定条件下才表现出来。
