Grimes A, Hearn C J, Lockhart P, Newgreen D F, Mercer J F
Murdoch Institute, Royal Children's Hospital, Parkville, Victoria, Australia.
Hum Mol Genet. 1997 Jul;6(7):1037-42. doi: 10.1093/hmg/6.7.1037.
The brindled mouse mutant (Mo(br)) is the closest animal model of the human genetic copper deficiency, Menkes disease, which is presumed to be due to a mutation at the X-linked mottled locus (Mo). The mutant mice are hypopigmented and die at around 15 days after birth, but can be saved by treatment with copper before the 10th postnatal day. Menkes disease has been shown to be due to mutations of the gene ATP7A which encodes P-type ATPase (referred to here as MNK). MNK is likely to function in copper efflux from cells, but the full range of its biological activity is not fully understood. The nature of the mutation in the brindled mouse is of importance in our understanding of the role of MNK and for devising treatment strategies for Menkes disease. Here we show that the brindled mouse has a deletion of two amino acids in a highly conserved, but functionally uncharacterized, region of Mnk. Comparison with the Ca ATPases suggests this region may be involved in conformational changes associated with the E1/E2 transition fundamental to the action of P-type ATPases. We also describe the first Western blot data for Mnk in tissues, and these show normal levels of Mnk in mutant and brindled kidneys but none in liver. In the kidney, immunohistochemistry demonstrated Mnk in the proximal and distal tubules, the distribution is identical in mutant and normal. This distribution is consistent with Mnk being involved in copper resorption from the urine.
花斑小鼠突变体（Mo(br)）是人类遗传性铜缺乏症——门克斯病最接近的动物模型，据推测该病是由X连锁斑驳位点（Mo）的突变所致。突变小鼠色素沉着不足，出生后约15天死亡，但在出生后第10天之前用铜治疗可挽救其生命。已证明门克斯病是由编码P型ATP酶（此处称为MNK）的ATP7A基因突变引起的。MNK可能在细胞铜流出中起作用，但其全部生物学活性尚未完全了解。花斑小鼠的突变性质对于我们理解MNK的作用以及制定门克斯病的治疗策略具有重要意义。在此我们表明，花斑小鼠在Mnk高度保守但功能未明确的区域缺失了两个氨基酸。与钙ATP酶的比较表明，该区域可能参与了与P型ATP酶作用所必需的E1/E2转变相关的构象变化。我们还描述了组织中Mnk的首次蛋白质印迹数据，这些数据显示突变型和花斑型肾脏中Mnk水平正常，但肝脏中未检测到。在肾脏中，免疫组织化学显示近端和远端小管中有Mnk，突变型和正常型的分布相同。这种分布与Mnk参与从尿液中重吸收铜一致。
