Timing is everything

Article Abstract:

GTP/GDP cycle of Rab proteins acts as a molecular timer that determine the frequency of docking process and membrane fusion by coordinating the protein interactions involved in docking. Rab proteins, a GTPase, is not a component of the protein complex on the vesicle and target membrane, involved in the membrane fusion, but acts as a molecular switch having active GTP-bound and inactive GDP-bound conformational states. Experiments using a mutant Rab show that Rab GTPase activity is independent of docking and fusion indicating that it is a timer which monitors pre-docking and pre-fusion events.

Reports, Physiological aspects, Proteins, Membrane fusion

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CD8 enhances formation of stable T-cell receptor/MHC class I molecule complexes

Article Abstract:

CD8 helps the formation and stabilization of T-cell antigen receptors (TCR) with the major histocompatibility complex (MHC). The binding of CD8 is unaffected by the MHC haplotype and the peptide content. TCR affinity for the specific ligand is increased by a reduced off rate in the presence of CD8 alpha homodimer or CD8 alpha beta heterodimer. CD8 is crucial for T-cell recognition and it may directly interact with the TCR. The stabilization is caused by either an energetically favourable interaction of TCR with MHC or an induced conformational change.

Research, Antigen receptors, T cell, T cell antigen receptors, Major histocompatibility complex

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Structure and mutational analysis of Rab GDP-dissociation inhibitor

Article Abstract:

The crystal structure of the bovine alpha-isoform of Rab GDP-dissociation inhibitor (GDI) indicates the presence of a small alpha-helical domain II and a large complex multisheet domain I. The organization of domain I is similar to that of the FAD-containing monooxygenases and oxidases. The binding of GDI to Rab proteins involves two regions at the top of GDI, whose sequences are highly conserved. The amino acid sequence of the alpha- and beta-isoforms of GDI is similar to that of the mammalian choroideraemia gene product and a related isoform.

Enzyme inhibitors

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