STRUCTURE AND FUNCTION OF PEPTIDE TRANSPORTERS

CD8+ T细胞（TCD8+）在控制病毒中起重要作用 感染. TCD8+识别来源于以下的8至10个残基的肽： 位于病毒感染细胞的胞质溶胶中的病毒蛋白。 这些 肽在与I类分子的复合物中被识别， 主要组织相容性复合体（MHC） 在过去的三年里， 发现MHC还编码两种分子，称为TAP 1和 TAP2，似乎特异性地从细胞质中转运肽 进入含有I类分子的细胞内区室。 已经发现TAP基因在人类中是多态性的，尽管对一个人来说， 远小于I类分子。存在这些 假定的肽泵及其多态性引起了许多 重要的问题：细胞中的泵位于何处？ 做 泵影响由I类分子呈递的肽的类型？ 泵是否与产生抗原肽的蛋白酶相连 在细胞质中 泵是如何工作的？ 有没有人 TAP基因突变导致的免疫缺陷 Can细胞 通过其他机制运输肽？ 为了帮助描述TAP基因的结构和功能，我们 将它们插入牛痘病毒中。 我们已经证明， 编码TAP 1的Vac重组体产生全功能基因，并且 已经发现由该重组体产生的TAP 1定位于 内质网，在那里它被糖基化。 我们提供了 重组体，其产生功能活性TAP 2。 我们还 检测了抗原转运蛋白的特异性。 我们发现 转运蛋白可以转运按类别呈递的确切肽 I分子。我们还检测了人类TAP2基因的表达是否 在小鼠细胞中， TCD8+的病毒蛋白。 我们发现人类TAP2基因的功能 以一种与其老鼠对应物难以区分的方式。 最后我们 已经探索了细胞中肽的呈递， 表达一个或两个TAP基因。

CD8+ T cells (TCD8+ ) play an important role in controlling virus infections. TCD8+ recognize peptides of 8 to 10 residues derived from viral proteins located in the cytosol of virus infected cells. These peptides are recognized in a complex with class I molecules encoded by the major histocompatibility complex (MHC). In the past 3 years it was discovered that the MHC also encodes two molecules, termed TAP1 and TAP2, that seem to specifically transport peptides from the cytosol into the intracellular compartment that contains class I molecules. TAP genes have been found to be polymorphic in humans, although to a far lesser extent than the class I molecules. The existence of these putative peptide pumps and their polymorphism raises a number of important questions: Where in the cells are the pumps located? Do the pumps influence the types of peptides presented by class I molecules? Are the pumps tethered to the proteases that produce antigenic peptides in the cytosol? How do the pumps work? Are there individuals with immune deficiencies based on mutations in the TAP genes? Can cells transport peptides via other mechanisms? To help characterize the structure and function of the TAP genes we have inserted them into vaccinia virus. We have demonstrated that a Vac recombinant encoding TAP1 produces a fully functional gene, and have found that TAP1 produced by this recombinant localizes to the endoplasmic reticulum where it is glycosylated. We produced a recombinant that produces a functionally active TAP2. We have also examined the specificity of the antigen transporters. We found that the transporters can transport the exact peptides presented by class I molecules. Also we examined whether expression of the human TAP2 gene in mouse cells adversely affects the ability of the cells to present viral proteins to TCD8+. We find that the human TAP2 gene functions in a indistinguishable manner from its mouse counterpart. Finally, we have explored the presentation of peptides in cells that fail to express one or both TAP genes.