3DKE

Polar and non-polar cavities in phage T4 lysozyme

Summary for 3DKE

• Entry DOI: 10.2210/pdb3dke/pdb
• Related: 181L 3DMV 3DMX 3DMZ 3DN0 3DN1 3DN2 3DN3 3DN4 3DN6 3DN8 3DNA
• Descriptor: Lysozyme, POTASSIUM ION, CHLORIDE ION, ... (9 entities in total)
• Functional Keywords: t4 lysozyme, cavity, experimental phases, antimicrobial, bacteriolytic enzyme, glycosidase, hydrolase
• Biological source: Bacteriophage T4
• Total number of polymer chains: 1
• Total formula weight: 19795.11

Authors

Liu, L.J.,Matthews, B.W. (deposition date: 2008-06-24, release date: 2008-11-25, Last modification date: 2021-10-20)

Primary citation

Liu, L.,Quillin, M.L.,Matthews, B.W.
Use of experimental crystallographic phases to examine the hydration of polar and nonpolar cavities in T4 lysozyme
Proc.Natl.Acad.Sci.USA, 105:14406-14411, 2008

PubMed Abstract: There is conflicting evidence as to whether cavities in proteins that are nonpolar and large enough to accommodate solvent are empty or are occupied by disordered water molecules. Here, we use multiple-wavelength x-ray data collected from crystals of the selenomethionine-substituted L99A/M102L mutant of T4 lysozyme to obtain a high-resolution electron density map free of bias that is unavoidably associated with conventional model-based structure determination and refinement. The mutant, L99A/M102L, has four cavities, two being polar in character and the other two nonpolar. Cavity 1 (polar, volume 45.2 A(3)) was expected to contain two well ordered water molecules, and this is confirmed in the experimental electron density map. Likewise, cavity 2 (polar, 16.9 A(3)) is confirmed to contain a single water molecule. Cavity 3 (nonpolar, 21.4 A(3)) was seen to be empty in conventional x-ray refinement, and this is confirmed in the experimental map. Unexpectedly, however, cavity 4 (nonpolar, volume 133.5 A(3)) was seen to contain diffuse electron density equivalent to approximately 1.5 water molecules. Although cavity 4 is largely nonpolar, it does have some polar character, and this apparently contributes to the presence of solvent. The cavity is large enough to accommodate four to five water molecules, and it appears that a hydrogen-bonded chain of three or more solvent molecules could occupy the cavity at a given time. The results are consistent with theoretical predictions that cavities in proteins that are strictly nonpolar will not contain solvent until the volume is large enough to permit mutually satisfying water-water hydrogen bonds.

PubMed: 18780783
DOI: 10.1073/pnas.0806307105

Experimental method

X-RAY DIFFRACTION (1.25 Å)