Influence of neurophysin residues 1-8 on the optical activity of neurophysin-peptide complexes. Direct evidence that the 1-8 sequence alters the environment of bound peptide.
Circular dichroism was used to compare the environment of peptides bound to native and des 1-8 neurophysin in order to further elucidate the role of the neurophysin 1-8 sequence in peptide-binding. A very large positive ellipticity (approximately 6000 deg cm2 dmol-1), shown earlier to be induced in tyrosine at position 2 of peptides bound to the native protein, was determined by the present study to be paralleled by similar induced changes in tyrosine at peptide position 1. Deletion of the neurophysin 1-8 sequence led to loss of half of the induced optical activity at peptide positions 1 and 2 and changes in binding-induced optical activity in the protein, the latter partially assignable to protein disulfides. In the mononitrated native and des 1-8 proteins, the optical activity of neurophysin Tyr-49, a residue at the peptide-binding site, was reduced by 80% in complexes of the des 1-8 protein relative to those of the native protein. The results suggest a role for neurophysin Arg-8 in modulating the optical activity at the binding site by directly placing a charge proximal to the binding site and/or by altering binding site conformation. The data provide the first unambiguous evidence of a difference in the environment of bound peptide between the native and des 1-8 proteins.
Breslow
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Department of Biochemistry, Cornell University Medical College, New York, NY.
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Hanna
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Laborde
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D001665:Binding Sites; D002942:Circular Dichroism; D009481:Neurophysins / Q000378:metabolism*; D010446:Peptide Fragments / Q000378:metabolism*; D010455:Peptides / Q000378:metabolism*; D011485:Protein Binding; D013329:Structure-Activity Relationship; D014443:Tyrosine / Q000378:metabolism
D009481:Neurophysins; D010446:Peptide Fragments; D010455:Peptides; D014443:Tyrosine