1L01

STRUCTURAL STUDIES OF MUTANTS OF THE LYSOZYME OF BACTERIOPHAGE T4. THE TEMPERATURE-SENSITIVE MUTANT PROTEIN THR157 (RIGHT ARROW) ILE

Summary for 1L01

• Entry DOI: 10.2210/pdb1l01/pdb
• Related: 1L02 1L03 1L04 1L05 1L06 1L07 1L08 1L09 1L10 1L11 1L12 1L13 1L14 1L15 1L16 1L17 1L18 1L19 1L20 1L21 1L22 1L23 1L24 1L25 1L26 1L27 1L28 1L29 1L30 1L31 1L32 1L33 1L34 1L35 1L36 2LZM
• Descriptor: T4 LYSOZYME (2 entities in total)
• Functional Keywords: hydrolase (o-glycosyl)
• Biological source: Enterobacteria phage T4
• Cellular location: Host cytoplasm : P00720
• Total number of polymer chains: 1
• Total formula weight: 18644.50

Authors

Dao-Pin, S.,Alber, T.,Matthews, B.W. (deposition date: 1988-02-05, release date: 1988-04-16, Last modification date: 2024-05-22)

Primary citation

Grutter, M.G.,Gray, T.M.,Weaver, L.H.,Wilson, T.A.,Matthews, B.W.
Structural studies of mutants of the lysozyme of bacteriophage T4. The temperature-sensitive mutant protein Thr157----Ile.
J.Mol.Biol., 197:315-329, 1987

PubMed Abstract: To understand the roles of individual amino acids in the folding and stability of globular proteins, a systematic structural analysis of mutants of the lysozyme of bacteriophage T4 has been undertaken. The isolation, characterization, crystallographic refinement and structural analysis of a temperature-sensitive lysozyme in which threonine 157 is replaced by isoleucine is reported here. This mutation reduces the temperature of the midpoint of the reversible thermal denaturation transition by 11 deg.C at pH 2.0. Electron density maps showing differences between the wild-type and mutant X-ray crystal structures have obvious features corresponding to the substitution of threonine 157 by isoleucine. There is little difference electron density in the remainder of the molecule, indicating that the structural changes are localized to the site of the mutation. High-resolution crystallographic refinement of the mutant lysozyme structure confirms that it is very similar to wild-type lysozyme. The largest conformational differences are in the gamma-carbon of residue 157 and in the side-chain of Asp159, which shift 1.0 A and 1.1 A, respectively. In the wild-type enzyme, the gamma-hydroxyl group of Thr157 participates in a network of hydrogen bonds. Substitution of Thr157 with an isoleucine disrupts this set of hydrogen bonds. A water molecule bound in the vicinity of Thr155 partially restores the hydrogen bond network in the mutant structure, but the buried main-chain amide of Asp159 is not near a hydrogen bond acceptor. This unsatisfied hydrogen-bonding potential is the most obvious reason for the reduction in stability of the temperature-sensitive mutant protein.

PubMed: 3681997
DOI: 10.1016/0022-2836(87)90126-4

Experimental method

X-RAY DIFFRACTION (1.7 Å)