Accumulating evidence indicates that nmda receptors are involved in many complex physiological and neuropathological mechanisms , such as neuronal developmental plasticity , long - term potentiation ( ltp ) , learning and memory , excitotoxicity and neurodegenerative diseases etc . three gene families that encode nmda receptor subunits have been identified : nr1 , nr2a - d , and nr3 subunit 已知nmda受体与许多复杂的生理和病理机制有关，如突触的可塑性、长时程增强作用( ltp ) 、学习和记忆、兴奋性神经毒性、神经退行性变性疾病等。已克隆到3个编码nmda受体亚单位蛋白的基因家族，即nr1 、 nr2和nr3 。
These proteins are ubiquitous in the plant kingdom where they form a multiple genetic family . they have been suggested to be involved in dif ferent aspects of plant physiology and cell biology through their ability to bind and / or carry lipophilic compounds , including the formation of cutin by transporting the hydrophobic cutin monomers to the apoplast and the defence of plants against pathogens as antimicrobial agents and in flowering 此外nsltp在植物体内广泛存在并由一个基因家族编码，由于它能结合和转运脂类物质，因此推测它可能参与植物体内许多不同的生理过程，如转运蜡质的角质单体到表皮细胞外侧，作为抑菌蛋白抵抗病原菌的入侵以及花粉和柱头的识别等。
Initially , a polyclonal antibodies was used to screen the cdna expression library to isolate pf40 gene from millet . sequence analysis revealed that the pf40 gene contained an open reading frame ( orf ) encoding a protein with 75 % - 35 % sequence identity to the zips ( zinc or iron transporter proteins ) gene family . software analysis of the pf40 gene character showed that pf40 protein had a eight trans - membrane region structure , pf40 protein was also rich in leucine ( 18 . 4 % ) and the protein was a hydrophobic protein 序列分析表明该基因具有一个开放阅读框( openreadingframe , orf ) : genbank中查询该基因编码的蛋白与zips ( zincorirontransporterproteins ，离子通道蛋白)基因家族的蛋白有75 - 35的相似性；软件的分析结果显示该基因编码的蛋白为一个有8个跨膜区的跨膜蛋白； pf40蛋白为疏水蛋白，以上的特征也许是pf40基因发挥作用的基础。
( 2 ) we have cloned 752bp fragment of mxnrampl gene from the genomic dna of malus xiaojinensis cheng et jiang by using common pcr method with primers designed according to the conserved domain sequences of plant nramp gene families . sequence analysis suggested that the predicted amino acid sequence of this fragment has 98 % and 83 % identities to the nramp gene fragment of wheat and osnramps of rice respectively ( 2 )根据植物nramp基因家族的功能保守区序列设计引物，通过常规pcr法从小金海棠基因组dna中扩增出了mxnramp1基因的752bp的特异性产物；序列分析表明，该片段所推导的氨基酸序列与小麦nramp基因片段(杂交用的探针片段)及水稻osnramp3基因分别具有98和83的同源性。
( 3 ) 490bp cdna fragment of fe ( ii ) - transporter gene mxlrtl was cloned by using common pcr method from iron - stressed root cdna library of malus xiaojinensis cheng et jiang with primers designed according to the conserved domain sequences of plant irt gene families . then we cloned the full cdna of mxlrtl gene by race method from this library with primers designed according to the sequence of 490bp cdna fragment ( 3 )根据植物irt基因家族的功能保守区序列设计引物，首先通过常规pcr法从缺铁胁迫处理的小金海棠根系cdna文库中克隆了fe ( ) -转运蛋白基因mxirt1的490bp的片段，然后根据测序结果设计引物，通过race法从该cdna文库中克隆了mxirt1基因的cdna全长。
However , amphioxus ubf80 also showed some unique characters such as its amino acid residues at sites 39 , 54 , 63 and 74 in the cep . it appears that amphioxus not only represents an organism tr ansitional from invertebrates to vertebrates in phylogeny but also a possible diverged form radiated from the chordate ancestor at early chordate evolution . the possibility that some mutations in ub genes have taken place in different lines early at the divergence of plants and animals is also discussed 发现文昌鱼a二phi尸rxv基因是具有线粒体和过氧化物酶体信号特征( mitochondrialandperoxisomalsortingsignals )的抗氧化物酶基因;通过序列比对，我们把尸rxv归为l一cys和2一cys之外的3一cys类，从而把尸rx基因家族的两种分类方法统一了起来。
