文章基本信息

标题：Peptide translocation by the lysosomal ABC transporter TAPL is regulated by coupling efficiency and activation energy
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作者：Christoph Bock ; Tina Zollmann ; Katharina-Astrid Lindt 等
期刊名称：Scientific Reports
电子版ISSN：2045-2322
出版年度：2019
卷号：9
期号：1
页码：1-12
DOI：10.1038/s41598-019-48343-6
出版社：Springer Nature
摘要：The lysosomal polypeptide transporter TAPL belongs to the superfamily of ATP-binding cassette transporters. TAPL forms a homodimeric transport complex, which translocates oligo- and polypeptides into the lumen of lysosomes driven by ATP hydrolysis. Although the structure and the function of ABC transporters were intensively studied in the past, details about the single steps of the transport cycle are still elusive. Therefore, we analyzed the coupling of peptide binding, transport and ATP hydrolysis for different substrate sizes. Although longer and shorter peptides bind with the same affinity and are transported with identical K m values, they differ significantly in their transport rates. This difference can be attributed to a higher activation energy for the longer peptide. TAPL shows a basal ATPase activity, which is inhibited in the presence of longer peptides. Uncoupling between ATP hydrolysis and peptide transport increases with peptide length. Remarkably, also the type of nucleotide determines the uncoupling. While GTP is hydrolyzed as good as ATP, peptide transport is significantly reduced. In conclusion, TAPL does not differentiate between transport substrates in the binding process but during the following steps in the transport cycle, whereas, on the other hand, not only the coupling efficiency but also the activation energy varies depending on the size of peptide substrate.