Raschke B C, Wolf A H
Pflanzenphysiologisches Institut der Universität, Göttingen, Germany.
Planta. 1996;200(1):78-84. doi: 10.1007/BF00196652.
We have determined the complete primary structure of a putative P-type Ca(2+)-ATPase from the unicellular, halotolerant alga Dunaliella bioculata. The protein (DBCA1) with a calculated molecular mass of 114 kDa and eight to ten putative transmembrane segments contains all amino acid motifs specific to the family of P-type ATPases. Highest homology scores were obtained by comparison with (sarco)endoplasmic reticulum-type plant and animal Ca(2+)-ATPases (54% identity, 70% similarity). In addition, all amino acids shown to be essential for Ca2+ transport in animal sarcoplasmic reticulum Ca(2+)-ATPases are preserved in DBCA1. Significantly lower homologies were found with animal plasma membrane Ca(2+)-ATPases (33% identity, 55% similarity), and the carboxyterminus of DBCA1 gave no indications of possible calmodulin-binding sites, characteristic of those enzymes. It is assumed that DBCA1 is a representative of the endomembrane class of Ca(2+)-ATPases. In Northern blot experiments with polyadenylated RNA, a 3.7-kb transcript was detected at levels which were very low compared with those of the plasma membrane H(+)-ATPase from D. bioculata (DBPMA1; Wolf et al., 1995, Plant Mol Biol 28: 657-666). Southern blot analyses suggest the existence of additional Ca(2+)-ATPase genes in the haploid genome of D. bioculata.
我们已经确定了单细胞耐盐藻类杜氏盐藻中一种假定的P型Ca(2+) -ATP酶的完整一级结构。该蛋白质（DBCA1）计算分子量为114 kDa，含有八到十个假定的跨膜片段，包含P型ATP酶家族特有的所有氨基酸基序。通过与（肌）内质网型动植物Ca(2+) -ATP酶比较获得了最高同源性分数（54% 同一性，70% 相似性）。此外，动物肌质网Ca(2+) -ATP酶中显示对Ca2+ 转运至关重要的所有氨基酸在DBCA1中都得以保留。与动物质膜Ca(2+) -ATP酶的同源性显著较低（33% 同一性，55% 相似性），并且DBCA1的羧基末端未显示出那些酶特有的可能钙调蛋白结合位点的迹象。据推测，DBCA1是内膜类Ca(2+) -ATP酶的一个代表。在使用聚腺苷酸化RNA的Northern印迹实验中，检测到一个3.7 kb的转录本，其水平与杜氏盐藻的质膜H(+) -ATP酶（DBPMA1；Wolf等人，1995年，《植物分子生物学》28: 657 - 666）相比非常低。Southern印迹分析表明在杜氏盐藻的单倍体基因组中存在其他Ca(2+) -ATP酶基因。
