Solution NMR evidence for a cis Tyr-Ala peptide group in the structure of [Pro93Ala]
 

Solution NMR evidence for a cis Tyr-Ala peptide group in the structure of [Pro93Ala] bovine pancreatic ribonuclease A.

Related Articles Solution NMR evidence for a cis Tyr-Ala peptide group in the structure of [Pro93Ala] bovine pancreatic ribonuclease A.

Protein Sci. 2000 Feb;9(2):421-6

Authors: Xiong Y, Juminaga D, Swapna GV, Wedemeyer WJ, Scheraga HA, Montelione GT

Proline peptide group isomerization can result in kinetic barriers in protein folding. In particular, the cis proline peptide conformation at Tyr92-Pro93 of bovine pancreatic ribonuclease A (RNase A) has been proposed to be crucial for chain folding initiation. Mutation of this proline-93 to alanine results in an RNase A molecule, P93A, that exhibits unfolding/refolding kinetics consistent with a cis Tyr92-Ala93 peptide group conformation in the folded structure (Dodge RW, Scheraga HA, 1996, Biochemistry 35:1548-1559). Here, we describe the analysis of backbone proton resonance assignments for P93A together with nuclear Overhauser effect data that provide spectroscopic evidence for a type VI beta-bend conformation with a cis Tyr92-Ala93 peptide group in the folded structure. This is in contrast to the reported X-ray crystal structure of [Pro93Gly]-RNase A (Schultz LW, Hargraves SR, Klink TA, Raines RT, 1998, Protein Sci 7:1620-1625), in which Tyr92-Gly93 forms a type-II beta-bend with a trans peptide group conformation. While a glycine residue at position 93 accommodates a type-II bend (with a positive value of phi93), RNase A molecules with either proline or alanine residues at this position appear to require a cis peptide group with a type-VI beta-bend for proper folding. These results support the view that a cis Pro93 conformation is crucial for proper folding of wild-type RNase A.

PMID: 10716195 [PubMed - indexed for MEDLINE]



Source: PubMed