Eitinger T, Friedrich B
Institut für Pflanzenphysiologie und Mikrobiologie, Freie Universität Berlin, Germany.
Mol Microbiol. 1994 Jun;12(6):1025-32. doi: 10.1111/j.1365-2958.1994.tb01090.x.
The gene hoxN of Alcaligenes eutrophus encodes a membrane protein with a molecular mass of 33.1 kDa that mediates energy-dependent uptake of nickel ions. Based on the hydrophobicity of the HoxN protein five, six, or seven transmembrane segments were predicted, depending on the algorithm used for computer analysis. To distinguish between these possibilities varying segments of the amino-terminal end of the transporter were fused to the Escherichia coli enzymes alkaline phosphatase (PhoA) or beta-galactosidase (LacZ). The enzymatic activity of 16 HoxN-PhoA and 15 HoxN-LacZ fusions was determined. On the assumption that PhoA fusions only exhibit high activity when fused to periplasmic domains of the target, while LacZ fusions are only active when oriented towards the cytoplasm, a two-dimensional model for the nickel transporter was developed. This model proposes that HoxN contains four periplasmic and four cytoplasmic regions, and seven transmembrane helices. The amino terminus is located in the cytoplasm, and the carboxyl terminus faces the periplasm.
嗜中温产碱杆菌的hoxN基因编码一种分子量为33.1 kDa的膜蛋白，该蛋白介导镍离子的能量依赖性摄取。根据HoxN蛋白的疏水性，预测有五个、六个或七个跨膜片段，这取决于用于计算机分析的算法。为了区分这些可能性，将转运蛋白氨基末端的不同片段与大肠杆菌酶碱性磷酸酶（PhoA）或β-半乳糖苷酶（LacZ）融合。测定了16个HoxN-PhoA和15个HoxN-LacZ融合蛋白的酶活性。假设PhoA融合蛋白只有在与靶标的周质结构域融合时才表现出高活性，而LacZ融合蛋白只有在朝向细胞质时才具有活性，由此建立了镍转运蛋白的二维模型。该模型表明，HoxN包含四个周质区域和四个细胞质区域，以及七个跨膜螺旋。氨基末端位于细胞质中，羧基末端面向周质。
