Biomaterial Database

Modeling protein stability: a theoretical analysis of the stability of T4 lysozyme mutants. 1997

D L Veenstra, and P A Kollman

University of California San Francisco, Department of Pharmaceutical Chemistry, 94143-0446, USA.

Free energy calculations were conducted to determine the relative stability of the unnatural amino acid mutants of T4 lysozyme norvaline (Nvl) and O-methyl-serine (Mse) and of alanine at residue 133, which is leucine in the native sequence. These calculations were performed both to assess the validity of the methodology and to gain a better understanding of the forces which contribute to protein stability. Peptides of different length were used to model the denatured state. Restraints were employed to force sampling of the side chain chi1 dihedral of the perturbed side chain, and the effect of protein repacking in response to mutation was studied through the use of different constraint sets. In addition, the convergence behavior and hysteresis of the simulations in the folded and unfolded states were determined. The calculated results agree well with experiment, + 1.84 versus + 1.56 kcal/mol for Mse-->Nvl and -3.48 versus -2.2 to -3.6 kcal/mol for Nvl-->Ala. We find that free energy calculations can provide useful insights to protein stability when conducted carefully on a well chosen system. Our results suggest that loss of packing interactions in the native state is a major source of destabilization for mutants which decrease the amount of buried nonpolar surface area and that subtle responses of the backbone affect the magnitude of the loss of stability. We show that the conformational freedom of the chi1 dihedral has a noticeable effect on protein stability and that the solvation of amino acid side chains is strongly influenced by interactions with the peptide backbone.

UI	MeSH Term	Description	Entries
D008958	Models, Molecular	Models used experimentally or theoretically to study molecular shape, electronic properties, or interactions; includes analogous molecules, computer-generated graphics, and mechanical structures.	Molecular Models,Model, Molecular,Molecular Model
D009113	Muramidase	A basic enzyme that is present in saliva, tears, egg white, and many animal fluids. It functions as an antibacterial agent. The enzyme catalyzes the hydrolysis of 1,4-beta-linkages between N-acetylmuramic acid and N-acetyl-D-glucosamine residues in peptidoglycan and between N-acetyl-D-glucosamine residues in chitodextrin. EC 3.2.1.17.	Lysozyme,Leftose,N-Acetylmuramide Glycanhydrolase,Glycanhydrolase, N-Acetylmuramide,N Acetylmuramide Glycanhydrolase
D011487	Protein Conformation	The characteristic 3-dimensional shape of a protein, including the secondary, supersecondary (motifs), tertiary (domains) and quaternary structure of the peptide chain. PROTEIN STRUCTURE, QUATERNARY describes the conformation assumed by multimeric proteins (aggregates of more than one polypeptide chain).	Conformation, Protein,Conformations, Protein,Protein Conformations
D003198	Computer Simulation	Computer-based representation of physical systems and phenomena such as chemical processes.	Computational Modeling,Computational Modelling,Computer Models,In silico Modeling,In silico Models,In silico Simulation,Models, Computer,Computerized Models,Computer Model,Computer Simulations,Computerized Model,In silico Model,Model, Computer,Model, Computerized,Model, In silico,Modeling, Computational,Modeling, In silico,Modelling, Computational,Simulation, Computer,Simulation, In silico,Simulations, Computer
D004795	Enzyme Stability	The extent to which an enzyme retains its structural conformation or its activity when subjected to storage, isolation, and purification or various other physical or chemical manipulations, including proteolytic enzymes and heat.	Enzyme Stabilities,Stabilities, Enzyme,Stability, Enzyme
D000595	Amino Acid Sequence	The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION.	Protein Structure, Primary,Amino Acid Sequences,Sequence, Amino Acid,Sequences, Amino Acid,Primary Protein Structure,Primary Protein Structures,Protein Structures, Primary,Structure, Primary Protein,Structures, Primary Protein
D013816	Thermodynamics	A rigorously mathematical analysis of energy relationships (heat, work, temperature, and equilibrium). It describes systems whose states are determined by thermal parameters, such as temperature, in addition to mechanical and electromagnetic parameters. (From Hawley's Condensed Chemical Dictionary, 12th ed)	Thermodynamic
D015202	Protein Engineering	Procedures by which protein structure and function are changed or created in vitro by altering existing or synthesizing new structural genes that direct the synthesis of proteins with sought-after properties. Such procedures may include the design of MOLECULAR MODELS of proteins using COMPUTER GRAPHICS or other molecular modeling techniques; site-specific mutagenesis (MUTAGENESIS, SITE-SPECIFIC) of existing genes; and DIRECTED MOLECULAR EVOLUTION techniques to create new genes.	Genetic Engineering of Proteins,Genetic Engineering, Protein,Proteins, Genetic Engineering,Engineering, Protein,Engineering, Protein Genetic,Protein Genetic Engineering
D016297	Mutagenesis, Site-Directed	Genetically engineered MUTAGENESIS at a specific site in the DNA molecule that introduces a base substitution, or an insertion or deletion.	Mutagenesis, Oligonucleotide-Directed,Mutagenesis, Site-Specific,Oligonucleotide-Directed Mutagenesis,Site-Directed Mutagenesis,Site-Specific Mutagenesis,Mutageneses, Oligonucleotide-Directed,Mutageneses, Site-Directed,Mutageneses, Site-Specific,Mutagenesis, Oligonucleotide Directed,Mutagenesis, Site Directed,Mutagenesis, Site Specific,Oligonucleotide Directed Mutagenesis,Oligonucleotide-Directed Mutageneses,Site Directed Mutagenesis,Site Specific Mutagenesis,Site-Directed Mutageneses,Site-Specific Mutageneses
D017122	Bacteriophage T4	Virulent bacteriophage and type species of the genus T4-like phages, in the family MYOVIRIDAE. It infects E. coli and is the best known of the T-even phages. Its virion contains linear double-stranded DNA, terminally redundant and circularly permuted.	Bacteriophage T2,Coliphage T2,Coliphage T4,Enterobacteria phage T2,Enterobacteria phage T4,Phage T2,Phage T4,T2 Phage,T4 Phage,Phage, T2,Phage, T4,Phages, T2,Phages, T4,T2 Phages,T2, Enterobacteria phage,T4 Phages