Effects of varying the local propensity to form secondary structure on the stability and folding kinetics of a rapid folding mixed alpha/beta protein: characterization of a truncation mutant of the N-terminal domain of the ribosomal protein L9.
The N-terminal domain of the ribosomal protein L9 forms a split betaalphabeta structure with a long C-terminal helix. The folding transitions of a 56 residue version of this protein have previously been characterized, here we report the results of a study of a truncation mutant corresponding to residues 1-51. The 51 residue protein adopts the same fold as the 56 residue protein as judged by CD and two-dimensional NMR, but it is less stable as judged by chemical and thermal denaturation experiments. Studies with synthetic peptides demonstrate that the C-terminal helix of the 51 residue version has very little propensity to fold in isolation in contrast to the C-terminal helix of the 56 residue variant. The folding rates of the two proteins, as measured by stopped-flow fluorescence, are essentially identical, indicating that formation of local structure in the C-terminal helix is not involved in the rate-limiting step of folding.
Luisi
D L
DL
Department of Chemistry, State University of New York at Stony Brook, Stony Brook, NY 11794-3400, USA.
Kuhlman
B
B
Sideras
K
K
Evans
P A
PA
Raleigh
D P
DP
D016009:Chi-Square Distribution; D002942:Circular Dichroism; D007700:Kinetics; D008958:Models, Molecular; D016296:Mutagenesis; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods; D010446:Peptide Fragments / Q000737:chemistry*; D017510:Protein Folding; D017433:Protein Structure, Secondary; D015203:Reproducibility of Results; D012269:Ribosomal Proteins / Q000737:chemistry*; D017384:Sequence Deletion; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
D010446:Peptide Fragments; D012269:Ribosomal Proteins; C049650:ribosomal protein L9