The NHB1 (N-terminal homology box 1) sequence in transcription factor Nrf1 is required to anchor it to the endoplasmic reticulum and also to enable its asparagine-glycosylation
The NHB1 (N-terminal homology box 1) sequence in transcription factor Nrf1 is required to anchor it to the endoplasmic reticulum and also to enable its asparagine-glycosylation
复制标题
DOI：
10.1042/bj20070761
复制
发表时间：
2007-12-01
影响因子：
4.1
通讯作者：
Hayes, John D.
中科院分区：
文献类型：
--
作者：
Zhang, Yiguo;Lucocq, John M.;Hayes, John D.
NrfI（核因子-红细胞2 p45亚基相关因子1）由其位于氨基酸1和124之间的NTD（N-末端结构域）负控制。该结构域包含一个富含亮氨酸的序列，称为NHB 1（N-末端同源盒1;残基11-30），其将NrfI连接到ER（内质网）。电泳将NrfI分离成两个主要条带，95和120 kDa。120-kDa NrfI形式代表仅存在于ER中的糖基化蛋白质，并且在用以下肽消化时转化为实质上更小的多肽：N-糖苷酶对于内切糖苷酶H。相比之下，95-kDa NrfI形式似乎没有糖基化，主要存在于细胞核中。NHB 1及其相邻残基符合经典的三重信号肽序列，包括n-、h-和c-区。将NrfI导向ER需要h区（残基11-22），但既不需要n区（残基1-10）也不需要c区（残基23-30）。将NrfI靶向ER是产生120-kDa糖基化蛋白所必需的。N-区和C-区是NrfI正确膜取向所必需的，因为残基2-10或23-30的缺失大大增加了其与ER的结合及其糖基化的程度。NHB 1不含信号肽酶切割位点，表明其作为ER锚序列。野生型NrfI通过其富含Asn/Ser/Thr的结构域（氨基酸296和403之间）进行糖基化，在NrfI（Delta 299-400）突变体中未观察到这种修饰。NrfI的糖基化并不需要将其保留在ER中。
NrfI(nuclear factor-erythroid 2 p45 subunit-related factor 1) is negatively controlled by its NTD (N-terminal domain) that lies between amino acids 1 and 124. This domain contains a leucine-rich sequence, called NHB1 (N-terminal homology box 1; residues 11-30), which tethers NrfI to the ER (endoplasmic reticulum). Electrophoresis resolved NrfI into two major bands of approx. 95 and 120 kDa. The 120-kDa NrfI form represents a glycosylated protein that was present exclusively in the ER and was converted into a substantially smaller polypeptide upon digestion with either peptide:N-glycosidase For endoglycosidase H. By contrast, the 95-kDa NrfI form did not appear to be glycosylated and was present primarily in the nucleus. NHB1 and its adjacent residues conform to the classic tripartite signal peptide sequence, comprising n-, h- and c-regions. The h-region (residues 11-22), but neither the n-region (residues 1-10) nor the c-region (residues 23-30), is required to direct NrfI to the ER. Targeting NrfI to the ER is necessary to generate the 120-kDa glycosylated protein. The n-region and c-region are required for correct membrane orientation of NrfI, as deletion of residues 2-10 or 23-30 greatly increased its association with the ER and the extent to which it was glycosylated. The NHB1 does not contain a signal peptidase cleavage site, indicating that it serves as an ER anchor sequence. Wild-type NrfI is glycosylated through its Asn/Ser/Thr-rich domain, between amino acids 296 and 403, and this modification was not observed in an NrfI(Delta 299-400) mutant. Glycosylation of NrfI was not necessary to retain it in the ER.