Monomeric (strept)avidin, even if it can be formed, seems to be thermodynamically unstable, as shown in ths recent paper below: J Biol Chem 2001 Mar 16;276(11):8219-24 Biotin induces tetramerization of a recombinant monomeric avidin. A model for protein-protein interactions. Laitinen OH, Marttila AT, Airenne KJ, Kulik T, Livnah O, Bayer EA, Wilchek M, Kulomaa MS. Department of Biological and Environmental Science, University of Jyvaskyla, FIN-40351, Jyvaskyla, Finland. Chicken avidin, a homotetramer that binds four molecules of biotin was converted to a monomeric form by successive mutations of interface residues to alanine. The major contribution to monomer formation was the mutation of two aspartic acid residues, which together account for ten hydrogen bonding interactions at the 1-4 interface. Mutation of these residues, together with the three hydrophobic residues at the 1-3 interface, led to stable monomer formation in the absence of biotin. Upon addition of biotin, the monomeric avidin reassociated to the tetramer, which exhibited properties similar to those of native avidin, with respect to biotin binding, thermostability, and protease resistance. To our knowledge, these unexpected results represent the first example of a small monovalent ligand that induces oligomerization of a monomeric protein. This study may suggest a biological role for low molecular weight ligands in inducing oligomerization and in maintaining the stability of multimeric protein assemblies. Ed Palmer wrote: > Dear Fellow Flowers, > > Does anyone have any information about monomeric avidin? (or monomeric streptavidin) i.e. an avidin that can bind just one biotin molecule? We are constructing a ligand for a T cell surface molecule which will have one biotin molecule attached. If there was a streptavidin-PE conjugate available that could bind just one biotin, then we might be able to accurately quantify how much ligand was bound using flow cytometry. > > Thanks for any information you might have. > > Ed Palmer > ______________________ > Ed Palmer M.D. Ph.D. > Laboratory of Transplantation Immunology > and Nephrology > Department of Research > University Hospital-Basel > Hebelstrasse 20 > CH-4031 Basel, Switzerland > e-mail: ed.palmer@unibas.ch > FAX: + 41 61 265 34 20
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