Domain-swap polymerization drives the self-assembly of the bacterial flagellar motor.

Large protein complexes assemble spontaneously, yet their subunits do not prematurely form unwanted aggregates. This paradox is epitomized in the bacterial flagellar motor, a sophisticated rotary motor and sensory switch consisting of hundreds of subunits. Here we demonstrate that Escherichia coli FliG, one of the earliest-assembling flagellar motor proteins, forms ordered ring structures via domain-swap polymerization, which in other proteins has been associated with uncontrolled and deleterious protein aggregation.

¹H, ¹⁵N and ¹³C assignments of an intramolecular LMO4-LIM1/CtIP complex.

LMO4 is a broadly expressed LIM-only protein that is involved in neural tube development and implicated in breast cancer. Here we report backbone and side chain NMR assignments for an engineered intramolecular complex of the N-terminal LIM domain from LMO4 tethered to residues 641-685 of C-terminal binding protein interacting protein (CtIP/RBBP8).

Protein-protein interactions: analysis of a false positive GST pulldown result.

One of the most common ways to demonstrate a direct protein-protein interaction in vitro is the glutathione-S-transferse (GST)-pulldown. Here we report the detailed characterization of a putative interaction between two transcription factor proteins, GATA-1 and Krüppel-like factor 3 (KLF3/BKLF) that show robust interactions in GST-pulldown experiments. Attempts to map the interaction interface of GATA-1 on KLF3 using a mutagenic screening approach did not yield a contiguous binding face on KLF3, suggesting that the interaction might be non-specific.

RING domain dimerization is essential for RNF4 function.

RNF4 [RING (really interesting new gene) finger protein 4] family ubiquitin ligases are RING E3 ligases that regulate the homoeostasis of SUMOylated proteins by promoting their ubiquitylation. In the present paper we report that the RING domain of RNF4 forms a stable dimer, and that dimerization is required for ubiquitin transfer. Our results suggest that the stability of the E2~ubiquitin thioester bond is regulated by RING domain dimerization.

Molecular analysis of the interaction between the hematopoietic master transcription factors GATA-1 and PU.1.

GATA-1 and PU.1 are transcription factors that control erythroid and myeloid development, respectively. The two proteins have been shown to function in an antagonistic fashion, with GATA-1 repressing PU.

Solution structure of a recombinant type I sculpin antifreeze protein.

We have determined the solution structure of rSS3, a recombinant form of the type I shorthorn sculpin antifreeze protein (AFP), at 278 and 268 K. This AFP contains an unusual sequence of N-terminal residues, together with two of the 11-residue repeats that are characteristic of the type I winter flounder AFP. The solution conformation of the N-terminal region of the sculpin AFP has been assumed to be the critical factor that results in recognition of different ice planes by the sculpin and flounder AFPs.

Crystal and solution structures of a superantigen from Yersinia pseudotuberculosis reveal a jelly-roll fold.

Superantigens are a class of microbial proteins with the ability to excessively activate T cells by binding to the T cell receptor. The staphylococcal and streptococcal superantigens are closely related in structure and possess an N-terminal domain that resembles an OB fold and a C-terminal domain similar to a beta-grasp fold. Yersinia pseudotuberculosis produces superantigens, YPMa, YPMb, and YPMc, which have no significant amino acid similarity to other proteins.