Lagarias D M, Wu S H, Lagarias J C
Section of Molecular and Cellular Biology, University of California, Davis 95616, USA.
Plant Mol Biol. 1995 Dec;29(6):1127-42. doi: 10.1007/BF00020457.
The phytochrome photoreceptor in the green alga Mesotaenium caldariorum is encoded by a small family of highly related genes. DNA sequence analysis of two of the algal phytochrome genes indicates an atypical gene structure with numerous long introns. The two genes, termed mesphy1a and mesphy1b, encode polypeptides which differ by one amino acid in the region of overlap that was sequenced. RT-PCR studies have established the intron-exon junctions of both genes and show that both are expressed. RNA blot analysis indicates a single transcript of ca. 4.1 kb in length. The deduced amino acid sequence of the mesphy1b gene reveals that the photoreceptor consists of 1142 amino acids, with an overall structure similar to other phytochromes. Phylogenetic analyses indicate that the algal phytochrome falls into a distinct subfamily with other lower plant phytochromes. Profile analysis of an internal repeat found within the central hinge region of the phytochrome polypeptide indicates an evolutionary relatedness to the photoactive yellow protein from the purple bacterium Ectothiorhodospira halophila, to several bacterial sensor kinase family members, and to a family of eukaryotic regulatory proteins which includes the period clock (per) and single-minded (sim) gene products of Drosophila. Since mutations which alter phytochrome activity cluster within the region delimited by these direct repeats (P.H. Quail et al., Science 268 (1995): 675-680), this conserved motif may play an important role in the signal transducing function of these disparate protein families.
绿藻嗜热微星藻中的光敏色素光受体由一个高度相关的小基因家族编码。对两个藻类光敏色素基因的DNA序列分析表明，它们具有非典型的基因结构，含有许多长内含子。这两个基因，即mesphy1a和mesphy1b，编码的多肽在测序的重叠区域仅相差一个氨基酸。RT-PCR研究确定了这两个基因的内含子-外显子连接，并表明它们都有表达。RNA印迹分析表明有一个约4.1kb长的单一转录本。mesphy1b基因推导的氨基酸序列显示，该光受体由1142个氨基酸组成，其整体结构与其他光敏色素相似。系统发育分析表明，藻类光敏色素与其他低等植物光敏色素属于一个不同的亚家族。对光敏色素多肽中央铰链区发现的一个内部重复序列的图谱分析表明，它与嗜盐外硫红螺菌的光活性黄色蛋白、几个细菌传感激酶家族成员以及一个真核调节蛋白家族存在进化相关性，该真核调节蛋白家族包括果蝇的周期时钟（per）和单-minded（sim）基因产物。由于改变光敏色素活性的突变集中在由这些直接重复序列界定的区域内（P.H.奎尔等人，《科学》268(1995):675 - 680），这个保守基序可能在这些不同蛋白质家族的信号转导功能中起重要作用。
