Conformational studies of N‐Tyr‐MIF‐1 in aqueous solution by 1H nuclear magnetic resonance spectroscopy

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Abstract
N-Tyr-MIF-1 (Tyr-Pro-Leu-Gly-NH2) is an endogenous brain peptide with multiple effects on animal behavior. However, there have been no studies on the conformation of this tetrapeptide. In this report, we studied the conformation of N-Tyr-MIF-1 in aqueous solution by conventional one-dimensional and two-dimensional (COSY and NOESY) 1H nuclear magnetic resonance spectroscopy at 300 MHz. A complete set of assignments for the resolved resonances and approximate assignments for the overlapping resonances were made. The results demonstrate that N-Tyr-MIF-1 is in slow exchange between two conformers, most likely determined by the cis and trans states of the proline residue. The minor conformation represents 30 ± 3% of the population over the temperature range from 3° to 73°. In the major conformation, the tyrosine aromatic ring appears to be close enough to interact directly with the proline pyrrolidine ring, as indicated by a strong temperature dependence of the proline CβH, CδH and CδH′ chemical shifts. In contrast, this interaction of the tyrosine and proline rings is not present in the minor conformation.