Molecular characterization of hpuAB, the haemoglobin-haptoglobin-utilization operon of Neisseria meningitidis
Molecular characterization of hpuAB, the haemoglobin-haptoglobin-utilization operon of Neisseria meningitidis
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DOI：
10.1046/j.1365-2958.1997.2501619.x
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发表时间：
1997-02-01
影响因子：
3.6
通讯作者：
Dyer, DW
中科院分区：
文献类型：
--
作者：
Lewis, LA;Gray, E;Dyer, DW
我们之前鉴定出 HpuB，一种 85 kDa Fe 抑制蛋白，需要利用血红蛋白和血红蛋白-触珠蛋白复合物中的 Fe 并与血红蛋白和血红蛋白-触珠蛋白复合物结合。 hpuB 基因从脑膜炎奈瑟菌 DNM2 菌株中克隆，预测的氨基酸序列表明 HpuB 是属于高亲和力转运蛋白 TonB 家族的外膜受体。在 hpuB 的 5' 位置发现了第二个开放阅读框，预计编码 34.8 kDa 脂蛋白，并将其命名为 hpuA。通过构建缺乏 HpuA 的突变体，在总膜蛋白制剂中鉴定出 HpuA。通过脑膜炎球菌的 [H-3]-棕榈酸标记证实了 HpuA 的酰化。共有启动子序列在 hpuB 的 5' 端不明显。 hpuA插入突变发挥了极性效应，消除了hpuB的表达，表明hpuA和hpuB是共转录的。 3.5kb 多顺反子 hpuAB mRNA 被鉴定并显示其转录受到铁的抑制。转录起始位点被鉴定为 hpuA 翻译起始位点 5' 33 个核苷酸，适当定位在共有启动子和铁吸收调节器 (Fur) 盒序列周围。该操纵子的结构表明 HpuA-HpuB 是一种双组分受体，类似于二分转铁蛋白受体 TbpB-TbpA。
We previously identified HpuB, an 85 kDa Fe-repressible protein required for utilization of Fe from, and binding to, haemoglobin and the haemoglobin-haptoglobin complex. The gene for hpuB was cloned from Neisseria meningitidis strain DNM2 and the predicted amino acid sequence indicates that HpuB is an outer membrane receptor belonging to the TonB family of high-affinity transport proteins. A second open reading frame, predicted to encode a 34.8 kDa lipoprotein, was discovered 5' to hpuB, and was designated hpuA. HpuA was identified in a total-membrane-protein preparation by construction of a mutant lacking HpuA. Acylation of HpuA was confirmed by [H-3]-palmitic acid labelling of meningococci. Consensus promoter sequences were not apparent 5' to hpuB. The hpuA insertion mutation exerted a polar effect, abolishing expression of hpuB, suggesting that hpuA and hpuB are co-transcribed. The 3.5kb polycistronic hpuAB mRNA was identified and shown to be transcriptionally repressed by iron. The transcriptional start site was identified 33 nucleotides 5' to the hpuA translational start site, appropriately positioned around consensus promoter and ferric uptake regulator (Fur)-box sequences. The structure of this operon suggests that HpuA-HpuB is a two-component receptor analogous to the bipartite transferrin receptor TbpB-TbpA.