AI Article Synopsis
- Met5-enkephalin, a pentapeptide, can adopt two distinct folded structures characterized by different beta-bend formations involving specific glycine and phenylalanine residues.
- One structure brings the first and fourth residues, Tyr 1 and Phe 4, close together, while the other keeps them farther apart.
- Using one-dimensional nuclear Overhauser effect (NOE) measurements, the proximity of Tyr 1 and Phe 4 was determined, supporting the presence of the Gly 2-Gly 3 beta-bend, which resembles the known structure of Leu5-enkephalin and relates to its biological activity.
Article Abstract
Met5-enkephalin-a pentapeptide (Tyr-Gly-Gly-Phe-Met)-can exist in two possible folded arrangements with a rigid two-hydrogen-bonded network. In one arrangement, a Gly 2-Gly 3 beta-bend is formed and in the other a Gly 3-Phe 4 beta-bend. The two conformations are distinguished by the spatial relation of Tyr 1 and Phe 4: in the Gly 2-Gly 3 beta-bend, Tyr 1 and Phe 4 can be brought close to each other while in the Gly 3-Phe 4 beta-bend they are far apart (greater than 5 A). We have utilized one-dimensional (1D) nuclear Overhauser effect (NOE) measurements between the ring protons of Tyr 1 and Phe 4 to determine their proximity. The NOE data clearly show that a pair protons, one each from Tyr 1 and Phe 4, are as close as 3.3 A while other inter-proton distances are beyond 4.5 A. Therefore, we propose the presence of a Gly 2-Gly 3 beta-bend (in which Tyr 1 and Phe 4 are spatially close) for Met5-enkephalin in solution. The structure of Met5-enkephalin in solution is very similar to the single crystal structure of Leu5-enkephalin and tends to explain the biological activity data of several modified enkephalins.
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| http://dx.doi.org/10.1016/0014-5793(86)80414-8 | DOI Listing |
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