Sánchez D, Ganfornina M D, Gutiérrez G, Bastiani M J
Biology Department, University of Utah, Salt Lake City 84112, USA.
Mol Biol Evol. 1998 Apr;15(4):415-26. doi: 10.1093/oxfordjournals.molbev.a025938.
Arthropodan hemocyanins, prophenoloxidases (PPOs), and insect hexamerins form a superfamily of hemolymph proteins that we propose to call the AHPH superfamily. The evolutionary and functional relationships of these proteins are illuminated by a new embryonic hemolymph protein (EHP) that is expressed during early stages of development in the grasshopper embryo. EHP is a 78-kDa soluble protein present initially in the yolk sac content, and later in the embryonic hemolymph. Protein purification and peptide sequencing were used to identify an embryonic cDNA clone coding for EHP. In situ hybridization identifies hemocytes as EHP-expressing cells. As deduced from the cDNA clone, EHP is a secreted protein with two potential glycosylation sites. Sequence analysis defines EHP as a member of the AHPH superfamily. Phylogenetic analyses with all the currently available AHPH proteins, including EHP, were performed to ascertain the evolutionary history of this protein superfamily. We used both the entire protein sequence and each of the three domains present in the AHPH proteins. The phylogenies inferred for each of the domains suggest a mosaic evolution of these protein modules. Phylogenetic and multivariate analyses consistently group EHP with crustacean hemocyanins and, less closely, with insect hexamerins, relative to cheliceratan hemocyanins and PPOs. The grasshopper protein rigorously preserves the residues involved in oxygen binding, oligomerization, and allosteric regulation of the oxygen transport proteins. Although insects were thought not to have hemocyanins, we propose that EHP functions as an oxygen transport or storage protein during embryonic development.
节肢动物血蓝蛋白、前酚氧化酶（PPO）和昆虫六聚蛋白构成了一个血淋巴蛋白超家族，我们提议将其称为AHPH超家族。一种新的胚胎血淋巴蛋白（EHP）揭示了这些蛋白质之间的进化和功能关系，该蛋白在蝗虫胚胎发育的早期阶段表达。EHP是一种78 kDa的可溶性蛋白，最初存在于卵黄囊内容物中，随后存在于胚胎血淋巴中。通过蛋白质纯化和肽测序鉴定出编码EHP的胚胎cDNA克隆。原位杂交确定血细胞为表达EHP的细胞。从cDNA克隆推导可知，EHP是一种具有两个潜在糖基化位点的分泌蛋白。序列分析将EHP定义为AHPH超家族的成员。对包括EHP在内的所有现有AHPH蛋白进行了系统发育分析，以确定该蛋白超家族的进化历史。我们使用了整个蛋白质序列以及AHPH蛋白中存在的三个结构域中的每一个。针对每个结构域推断的系统发育表明这些蛋白质模块的镶嵌进化。系统发育和多变量分析一致地将EHP与甲壳类血蓝蛋白归为一组，与昆虫六聚蛋白的关系稍远，相对于螯肢动物血蓝蛋白和PPO。蝗虫蛋白严格保留了与氧结合、寡聚化以及氧运输蛋白的变构调节有关的残基。尽管昆虫被认为没有血蓝蛋白，但我们认为EHP在胚胎发育过程中作为一种氧运输或储存蛋白发挥作用。
