1eeq
M4L/Y(27D)D/T94H Mutant of LEN
Structural highlights
FunctionKV401_HUMAN V segment of the variable domain of immunoglobulins light chain that participates in the antigen recognition (PubMed:24600447). Immunoglobulins, also known as antibodies, are membrane-bound or secreted glycoproteins produced by B lymphocytes. In the recognition phase of humoral immunity, the membrane-bound immunoglobulins serve as receptors which, upon binding of a specific antigen, trigger the clonal expansion and differentiation of B lymphocytes into immunoglobulins-secreting plasma cells. Secreted immunoglobulins mediate the effector phase of humoral immunity, which results in the elimination of bound antigens (PubMed:20176268, PubMed:22158414). The antigen binding site is formed by the variable domain of one heavy chain, together with that of its associated light chain. Thus, each immunoglobulin has two antigen binding sites with remarkable affinity for a particular antigen. The variable domains are assembled by a process called V-(D)-J rearrangement and can then be subjected to somatic hypermutations which, after exposure to antigen and selection, allow affinity maturation for a particular antigen (PubMed:17576170, PubMed:20176268).[1] [2] [3] [4] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedWe have examined the influence of surface hydrogen bonds on the stability of proteins by studying the effects of mutations of human immunoglobulin light chain variable domain (V(L)). In addition to the variants Y27dD, N28F, and T94H of protein kappa IV Len that were previously described, we characterized mutants M4L, L27cN, L27cQ, and K39T, double mutant M4L/Y27dD, and triple mutant M4L/Y27dD/T94H. The triple mutant had an enhanced thermodynamic stability of 4.2 kcal/mol. We determined the structure of the triple mutant by x-ray diffraction and correlated the changes in stability due to the mutations with changes in the three-dimensional structure. Y27dD mutant had increased stability of Len by 2.7 kcal/mol, a large value for a single mutation. Asp27d present in CDR1 formed hydrogen bonds with the side-chain and main-chain atoms within the loop. In the case of the K39T mutant, which reduces stability by 2 kcal/mol, Lys39 in addition to forming a hydrogen bond with a carbonyl oxygen of a neighboring loop may also favorably influence the surface electrostatics of the molecule. We showed that hydrogen bonds between residues in surface loops can add to the overall stability of the V(L) domains. The contribution to stability is further increased if the surface residue makes more than one hydrogen bond or if it forms a hydrogen bond between neighboring turns or loops separated from each other in the amino acid sequence. Based on our experiments we suggest that stabilization of proteins might be systematically accomplished by introducing additional hydrogen bonds on the surface. These substitutions are more straightforward to predict than core-packing interactions and can be selected to avoid affecting the protein's function. Increasing protein stability by polar surface residues: domain-wide consequences of interactions within a loop.,Pokkuluri PR, Raffen R, Dieckman L, Boogaard C, Stevens FJ, Schiffer M Biophys J. 2002 Jan;82(1 Pt 1):391-8. PMID:11751325[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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