ActA and human zyxin harbour Arp2/3-independent actin-polymerization activity.

The actin cytoskeleton is a dynamic network that is composed of a variety of F-actin structures. To understand how these structures are produced, we tested the capacity of proteins to direct actin polymerization in a bead assay in vitro and in a mitochondrial-targeting assay in cells. We found that human zyxin and the related protein ActA of Listeria monocytogenes can generate new actin structures in a vasodilator-stimulated phosphoprotein-dependent (VASP) manner, but independently of the Arp2/3 complex.

Targeting of zyxin to sites of actin membrane interaction and to the nucleus.

The localization of proteins to particular intracellular compartments often regulates their functions. Zyxin is a LIM protein found prominently at sites of cell adhesion, faintly in leading lamellipodia, and transiently in cell nuclei. Here we have performed a domain analysis to identify regions in zyxin that are responsible for targeting it to different subcellular locations.

LPP, an actin cytoskeleton protein related to zyxin, harbors a nuclear export signal and transcriptional activation capacity.

The LPP gene is the preferred translocation partner of the HMGIC gene in a subclass of human benign mesenchymal tumors known as lipomas. Here we have characterized the LPP gene product that shares 41% of sequence identity with the focal adhesion protein zyxin. LPP localizes in focal adhesions as well as in cell-to-cell contacts, and it binds VASP, a protein implicated in the control of actin organization.

Association of myosin I alpha with endosomes and lysosomes in mammalian cells.

Myosin Is, which constitute a ubiquitous monomeric subclass of myosins with actin-based motor properties, are associated with plasma membrane and intracellular vesicles. Myosin Is have been proposed as key players for membrane trafficking in endocytosis or exocytosis. In the present paper we provide biochemical and immunoelectron microscopic evidence indicating that a pool of myosin I alpha (MMIalpha) is associated with endosomes and lysosomes.

Evidence for post-transcriptional regulation of the synthesis of the Escherichia coli HlyB haemolysin translocator and production of polyclonal anti-HlyB antibody.

Extensive attempts were made to overexpress the Escherichia coli haemolysin translocator protein HlyB, and HlyB fragments, utilising high copy number plasmids or hlyB expressed from strong promoters including lambda PR, ptrp and the T7 promoter. Analysis of both cytoplasmic and membrane fractions failed to detect any overexpression of the protein, although all the constructs showed biological activity and there was no evidence of HlyB-induced toxicity. In some constructs, the effect of removing a stem-loop structure, immediately upstream of the start codon and implicated in rho-independent termination of transcription, was tested but this did not lead to over-expression.