Biomedical subjects

G Kalhammer

Publications and source records attributed to G Kalhammer.

2 recordsLinked to original sources

PubMed2000

Unconventional myosins.

Myosins constitute a large superfamily of F-actin-based motor proteins found in many organisms from yeast to humans. A phylogenetic comparison of their head sequences has allowed them to be grouped into 15 different classes. Unconventional myosins can be monomeric or dimeric, but are thought not to form filaments, unlike conventional myosin. The double-headed class-V myosins are good candidates for transporting vesicles, organelles and (mRNA) particles along actin filaments. Class-I myosins are involved in membrane dynamics and actin organization at the cell cortex, thus affecting cell migration, endocytosis, pinocytosis and phagocytosis. A class-III myosin from Drosophila is required for phototransduction and maintenance of the rhabdomere. Class-IX myosins negatively regulate the small G-protein Rho, a signalling molecule that regulates the organization of the actin cytoskeleton. Protein kinases that are regulated by members of the Rho small G-protein family regulate the motor activities of different myosins.

Animals↗

PubMed1997

Ras-binding domains: predicting function versus folding.

Ras interacts with a number of effector molecules to achieve its prolific signalling. Based on iterative sequence profile and motif searches of databases a novel family of Ras-binding domains was recently identified (Ponting and Benjamin, Trends Biochem. Sci. 21: 422-425, 1996). Among them the rat unconventional myosin and Rho-GTPase-activating protein myr 5 was predicted to contain a Ras-binding domain at its N-terminus. Here we report that direct binding experiments between the proposed Ras-binding domain of myr 5 and Ras failed to demonstrate any interaction. Molecular modelling suggests that this domain in myr 5 adopts a similar folding topology as the Ras-binding domain of Raf kinase. However, unlike the Ras-binding domain of Raf kinase, the myr 5 domain lacks the positive surface charges necessary for binding the negatively charged Ras contact site. This result exemplifies the functional diversity of similar structures and suggests that the identified Ras-binding motif does not reliably predict Ras-binding domains.

Animals↗