Ortiz D F, Kreppel L, Speiser D M, Scheel G, McDonald G, Ow D W
Plant Gene Expression Center, US Department of Agriculture, Albany, CA 94710.
EMBO J. 1992 Oct;11(10):3491-9. doi: 10.1002/j.1460-2075.1992.tb05431.x.
In response to heavy metal stress, plants and certain fungi, such as the fission yeast Schizosaccharomyces pombe, synthesize small metal-binding peptides known as phytochelatins. We have identified a cadmium sensitive S. pombe mutant deficient in the accumulation of a sulfide-containing phytochelatin-cadmium complex, and have isolated the gene, designated hmt1, that complements this mutant. The deduced protein sequence of the hmt1 gene product shares sequence identity with the family of ABC (ATP-binding cassette)-type transport proteins which includes the mammalian P-glycoproteins and CFTR, suggesting that the encoded product is an integral membrane protein. Analysis of fractionated fission yeast cell components indicates that the HMT1 polypeptide is associated with the vacuolar membrane. Additionally, fission yeast strains harboring an hmt1-expressing multicopy plasmid exhibit enhanced metal tolerance along with a higher intracellular level of cadmium, implying a relationship between HMT1 mediated transport and compartmentalization of heavy metals. This suggests that tissue-specific overproduction of a functional hmt1 product in transgenic plants might be a means to alter the tissue localization of these elements, such as for sequestering heavy metals away from consumable parts of crop plants.
作为对重金属胁迫的响应，植物和某些真菌，如裂殖酵母粟酒裂殖酵母，会合成称为植物螯合肽的小金属结合肽。我们鉴定出了一种对镉敏感的粟酒裂殖酵母突变体，该突变体在含硫化物的植物螯合肽 - 镉复合物的积累方面存在缺陷，并分离出了一个名为hmt1的基因，该基因可补充此突变体。hmt1基因产物的推导蛋白质序列与ABC（ATP结合盒）型转运蛋白家族具有序列同源性，该家族包括哺乳动物的P - 糖蛋白和CFTR，这表明编码产物是一种整合膜蛋白。对分离的裂殖酵母细胞成分的分析表明，HMT1多肽与液泡膜相关。此外，携带表达hmt1的多拷贝质粒的裂殖酵母菌株表现出增强的金属耐受性以及更高的细胞内镉水平，这意味着HMT1介导的转运与重金属的区室化之间存在关联。这表明在转基因植物中组织特异性过量生产功能性hmt1产物可能是改变这些元素组织定位的一种手段，例如将重金属从农作物的可食用部分隔离。
