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Protein Complex Assembly

Protein Complex Assembly

Proteins can form homomeric complexes with another unit of the same protein or heteromeric complexes with different types. Most protein complexes self-assemble spontaneously via ordered pathways, while some proteins need assembly factors that guide their proper assembly. Despite the crowded intracellular environment, proteins usually interact with their correct partners and form functional complexes.
Many viruses self-assemble into a fully functional unit using the infected host cell to...

Assembly of Cytoskeletal Filaments

Assembly of Cytoskeletal Filaments

Cytoskeletal filaments are polymeric forms of smaller protein subunits. However, individual cytoskeletal filaments may easily disassemble or associate with other similar filaments to form rigid structures. Microfilaments, made of actin monomers, rely on actin-binding proteins to form bundles and create networks of individual actin filaments. Microtubules rely on microtubule-associated proteins (MAPs) to form sturdy cylindrical structures. However, the proteins involved in forming complex...

Generation of Straight or Branched Actin Filaments

Generation of Straight or Branched Actin Filaments

The straight or branched structure formation of actin filaments is controlled by nucleating proteins such as the formins and Arp2/3 complex. Formin-mediated assembly results in straight filaments, whereas Arp2/3 protein complex-mediated assembly results in branched actin filaments.
Arp2/3 Complex
Arp2/3 complex is a seven-subunit complex consisting of two proteins similar to actin- Arp2 and Arp3, and five other subunits that help keep Arp2 and Arp3 inactive. When required, the complex is...

Formation of Higher-order Actin Filaments

Formation of Higher-order Actin Filaments

The polymerization of G-actin monomers into filamentous F-actin is a multi-step process. Once the F-actins are formed, they can bundle together in different arrangements to form higher-order networks and regulate cellular functions. Common examples include the formation of lamellipodia and filopodia at the cell's leading edge by actin reorganization in a migrating cell. The microvilli on the brush border epithelial cells are also formed through the F-actin network.
The high-order actin networks...

Coat Assembly and GTPases

Coat Assembly and GTPases

Vesicles incorporate different coat protein subunits in different cell locations, which changes the properties of the coat, such as the shape and geometry of the transport vesicles. Thus, vesicle coat proteins also play a significant role in cargo selection.
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Assembly of Signaling Complexes

Assembly of Signaling Complexes

Multiprotein signaling complexes are formed in a dynamic process involving protein-protein interactions at the cytoplasmic domain of transmembrane receptors or enzymatic and non-enzymatic proteins associated with the receptor. These complexes ensure the activation and propagation of intracellular signals that regulate cell functions.
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A Guide to Production, Crystallization, and Structure Determination of Human IKK1/α

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Structures of dimeric GIT1 and trimeric beta-PIX and implications for GIT-PIX complex assembly.

Oliver Schlenker¹, Katrin Rittinger

¹Medical Research Council National Institute for Medical Research, The Ridgeway, London, UK.

Journal of Molecular Biology

|January 13, 2009

Summary

This summary is machine-generated.

G protein-coupled receptor kinase-interacting protein (GIT) and p21-activated kinase-interacting exchange factor (PIX) proteins form a pentameric complex. This GIT1-beta-PIX complex structure reveals insights into multiprotein signaling assemblies and their regulation.

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Self-Assembly of Gamma-Modified Peptide Nucleic Acids into Complex Nanostructures in Organic Solvent Mixtures

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Published on: June 26, 2020

Area of Science:

Molecular and Cellular Biology
Structural Biology
Biochemistry

Background:

G protein-coupled receptor kinase-interacting protein (GIT) and p21-activated kinase-interacting exchange factor (PIX) proteins are crucial scaffolds in cellular signaling.
These proteins integrate pathways involving Arf and Rho GTPases, regulating key processes like cell migration and polarity.
The GIT1-beta-PIX complex formation is mediated by specific binding domains and is essential for their physiological functions.

Purpose of the Study:

To elucidate the molecular architecture of the GIT1-beta-PIX complex.
To understand the role of oligomerization in GIT and PIX protein function.
To determine the stoichiometry and structural basis of GIT1-beta-PIX complex formation.

Main Methods:

X-ray crystallography was used to determine the structures of the coiled-coil (CC) domains of GIT1 and beta-PIX.
Hydrodynamic studies were employed to analyze protein complex formation and stoichiometry.
Biochemical assays were used to investigate binding interactions and complex assembly.

Main Results:

The crystal structure revealed that the GIT1 CC domain forms a parallel dimer.
Unexpectedly, the beta-PIX CC region forms a parallel trimer, challenging previous dimeric models.
Dimeric GIT1 and trimeric beta-PIX assemble into a high-affinity heteropentameric complex.

Conclusions:

The GIT1-beta-PIX complex exhibits an unusual pentameric stoichiometry, with a 2:3 ratio of GIT1 to beta-PIX.
This structural insight into the GIT1-beta-PIX complex provides a foundation for understanding oligomerization-dependent signaling.
The findings offer a deeper understanding of the architecture of large signaling complexes involving GIT1 and beta-PIX.