Báo cáo khoa học: The distinct nucleotide binding states of the transporter associated with antigen processing (TAP) are regulated by the nonhomologous C-terminal tails of TAP1 and TAP2

The Distinct Nucleotide Binding States of the Transporter Associated with Antigen Processing (TAP) are Regulated by the Nonhomologous C-terminal Tails of TAP1 and TAP2

Authors: Hicham Bouabe, Michael R. Knittler

Field: Genetics, University of Cologne, Germany

Document Content:

This document investigates the distinct nucleotide binding states of the transporter associated with antigen processing (TAP), a crucial protein complex responsible for delivering peptides into the endoplasmic reticulum for binding to major histocompatibility complex class I molecules. The study focuses on how the nonhomologous C-terminal tails of TAP1 and TAP2 regulate the intrinsic nucleotide binding properties of their respective nucleotide binding domains (NBDs). Through the generation and analysis of chimeric TAP1 and TAP2 polypeptides, the research demonstrates that these C-terminal tails play a critical regulatory role in coordinating nucleotide binding and ATP hydrolysis by TAP. The findings suggest that the C-terminal tail of TAP2 is particularly important for functional transport by regulating ATP binding, and that ATP binding to NBD2 prevents simultaneous ATP uptake by TAP1. This work elucidates a key mechanism in the functioning of TAP, contributing to our understanding of antigen presentation.

Detailed Table of Contents:

• Introduction
• Materials and Methods
• Cell lines and cell culture
• Cloning and expression of chimeric TAP1 and TAP2 chains
• Antibodies
• Immunoprecipitation and Western blotting
• Transport assay and peptide cross-linking
• Nucleotide binding assays
• Preparation of microsomal membranes
• Flow cytometry
• Results
• The nonhomologous C-terminal tails of the NBDs control the distinctive nucleotide binding properties of TAP1 and TAP2
• Functional correlation between the C-terminal regulated nucleotide binding and the transport activity of TAP
• The ability to exchange ADP for ATP is a prerequisite for the function of the TAP-NBDs
• TAP2 exerts allosteric control over the nucleotide binding of TAP1
• The C-terminal tail of the NBD2 is essential for ATP binding and the catalytic function of TAP
• Discussion
• Acknowledgements
• References