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Structure of Porins

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Mitochondria, chloroplasts, and gram-negative bacteria have transmembrane, beta-barrel proteins called porins to mediate the free diffusion of ions and metabolites across the membrane. Mitochondrial porin precursors contain conserved amino acid sequences called beta signals at their C-terminal. Beta signals have a motif of PoXGXXHyXHy (Po-Polar, X-Any amino acid, G-Glycine, Hy-LargeHydrophobic), which are crucial for precursor recognition to initiate precursor assembly. Beta-barrel precursors...

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Protein Folding

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Related Experiment Video

Updated: Jul 15, 2026

X-Ray Crystallography to Study the Oligomeric State Transition of the Thermotoga maritima M42 Aminopeptidase TmPep1050

X-Ray Crystallography to Study the Oligomeric State Transition of the Thermotoga maritima M42 Aminopeptidase TmPep1050

Published on: May 13, 2020

Structural basis for PRYSPRY-mediated tripartite motif (TRIM) protein function.

Leo C James¹, Anthony H Keeble, Zahra Khan

¹Protein and Nucleic Acid Chemistry Division, Medical Research Council Laboratory of Molecular Biology, Cambridge CB2 2QH, UK. lcj@mrc-lmb.cam.ac.uk

Proceedings of the National Academy of Sciences of the United States of America

|April 3, 2007

Summary

The PRYSPRY domain of TRIM proteins is key to their diverse functions. Specific binding sites control TRIM21-IgG interactions, impacting viral restriction and autoimmune diseases like familial Mediterranean fever.

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Last Updated: Jul 15, 2026

X-Ray Crystallography to Study the Oligomeric State Transition of the Thermotoga maritima M42 Aminopeptidase TmPep1050

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Optimized Protocol for the Extraction of Proteins from the Human Mitral Valve

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The Development and Application of Biophysical Assays for Evaluating Ternary Complex Formation Induced by Proteolysis Targeting Chimeras (PROTACS)

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Published on: January 12, 2024

Area of Science:

Immunology
Structural Biology
Genetics

Background:

The human tripartite motif (TRIM) family has 70 members with conserved domains but varied roles.
Key members include HIV restriction factor TRIM5alpha, TRIM20 (pyrin) involved in familial Mediterranean fever, and TRIM21.

Purpose of the Study:

To elucidate the role of the C-terminal PRYSPRY domain in mediating diverse TRIM protein functions.
To characterize the structural basis of TRIM21 binding to IgG Fc and its functional implications.

Main Methods:

X-ray crystallography to determine the structure of TRIM21 PRYSPRY bound to IgG Fc.
Alanine scanning mutagenesis to identify critical residues in the binding interface.
Functional assays to assess viral restriction and disease association.

Main Results:

The crystal structure revealed a canonical binding interface with two pockets formed by antibody-like loops.
Hot-spot residues were identified that mediate TRIM21-Fc binding, HIV/murine leukemia virus restriction by TRIM5alpha, and familial Mediterranean fever in TRIM20.
TRIM21 PRYSPRY acts as a superantigen, similar to bacterial protein A, by binding IgG Fc.

Conclusions:

The PRYSPRY domain is a versatile functional module across the TRIM family.
TRIM21's superantigenic activity and IgG Fc binding mechanism contribute to autoimmune disease pathogenesis through immune complex formation.