Membrane proteins on the move.

The Keystone Symposium on Membrane protein structure/function relationships was held on 5-11 March 2001 in Tahoe City, California, USA.     

Predicting antigenic sites on proteins.

The ability to predict antigenic sites on proteins is of major importance for the production of synthetic peptide vaccines and synthetic peptide probes of antibody structure. Many predictive methods, based on various assumptions about the nature of the antigenic response have been proposed and tested. This review will discuss the principles underlying the various approaches to predicting antigenic sites and will attempt to answer the question of how well they work.     

Actin-binding proteins.

Much new information on the sequence, structure, and function of filament crosslinking, capping, and severing proteins is now known. Other significant findings include identification of a new abundant monomer-sequestering protein in platelets, and evidence that many actin-binding proteins interact with phosphoinositides and that this interaction may have metabolic consequences.     

Cobalt proteins.

In the form of vitamin B12, cobalt plays a number of crucial roles in many biological functions. However, recent studies have provided information on the biochemistry and bioinorganic chemistry of several proteins containing cobalt in a form other than that in the corrin ring of vitamin B12. To date, eight noncorrin-cobalt-containing enzymes (methionine aminopeptidase, prolidase, nitrile hydratase, glucose isomerase, methylmalonyl-CoA carboxytransferase, aldehyde decarbonylase, lysine-2,3-aminomutase, and bromoperoxidase) have been isolated and characterized. A cobalt transporter is involved in the metallocenter biosynthesis of the host cobalt-containing enzyme, nitrile hydratase. Understanding the differences between cobalt and nickel transporters might lead to drug development for gastritis and peptic ulceration.     

Adaptor-related proteins.

Two new adaptor-related protein complexes, AP-3 and AP-4, have recently been identified, and both have been implicated in protein sorting at the trans-Golgi network (TGN) and/or endosomes. In addition, two families of monomeric proteins with adaptor-related domains, the GGAs and the stoned B family, have also been identified and shown to act at the TGN and plasma membrane, respectively. Together with the two conventional adaptors, AP-1 and AP-2, these proteins may act to direct different types of cargo proteins to different post-Golgi membrane compartments.     

Biosensors based on membrane transport proteins.

We propose a novel class of biosensors based on membrane bound receptors or transport proteins as the sensing element. The protein is incorporated in a planar lipid bilayer which covers the transducer. The transducer may detect an electric current, a voltage, or a change in fluorescence. A prototype lactose sensor is presented which consists of a quartz slide covered by a lipid membrane containing the protein lactose permease from Escherichia coli. This protein is a lactose/H+ cotransporter, hence lactose in the external medium initiates lactose/H+ cotransport across the lipid membrane. This leads to a rise in proton concentration in the small volume between the lipid membrane and the quartz surface which can be detected by a pH-sensitive fluorescence dye.