INTERNAL BETA-TURN HYDRATION - CRYSTALLOGRAPHIC EVIDENCE AND MOLECULAR-DYNAMICS SIMULATION

Citation
A. Dinola et al., INTERNAL BETA-TURN HYDRATION - CRYSTALLOGRAPHIC EVIDENCE AND MOLECULAR-DYNAMICS SIMULATION, Journal of physical chemistry, 99(23), 1995, pp. 9625-9631
Citations number
36
Categorie Soggetti
Chemistry Physical
ISSN journal
00223654
Volume
99
Issue
23
Year of publication
1995
Pages
9625 - 9631
Database
ISI
SICI code
0022-3654(1995)99:23<9625:IBH-CE>2.0.ZU;2-I
Abstract
The X-ray structure analysis of the monohydrate phase of the peptide F or-Met-Leu-Delta(2)Phe-Phe-OMe has revealed that the type-II beta-turn supported by the 4 --> 1 H-bond, expected for the backbone containing the alpha,beta-unsaturated residue Delta(2)Phe, has been modified by the water molecule. The water prevents the 4 --> 1 H-bond between Met CO and Phe NH groups, forming a H-bonded bridge between these groups a nd causing significant modification of the secondary structure. The hy drated beta-turn found in the crystal can be an interesting static mod el useful for the comprehension of the internal hydration mechanism of beta-turns, secondary structures largely present in globular proteins , but generally distributed only on their surface. The internal hydrat ion, with a H-bonded water bridge and modification of the secondary st ructure, differs from the most common external hydration, where the ex ternally bound water does not cause modification of secondary structur e. In order to verify whether the internally hydrated beta-turn could be found even in solution, a molecular dynamics simulation has been pe rformed. The results show that the two forms, the beta-turn with the 4 --> 1 H-bond and that with the H-bonded water bridge, do not differ s ubstantially in their energy values. Moreover, no high-energy barrier prevents interconversion between the two forms. The internal beta-turn hydration presents strong analogies with the internally hydrated heli cal peptide segments found in oligopeptides and proteins.