Folding defects caused by single amino acid substitutions in a subunit are not alleviated by assembly.
Significant stabilization of a protein often occurs when it is assembled into an oligomer. Bacteriophage P22 contains 420 monomers of coat protein that are stabilized by the assembly and maturation processes. The effects of eight single amino acid substitutions in coat protein that each cause a temperature-sensitive-folding defect were investigated to determine if the conformational differences previously observed in the monomers could be alleviated by assembly or maturation. Several techniques including differential scanning calorimetry, heat-induced expansion, urea denaturation, and sensitivity to protease digestion were used to explore the effects of the amino acid substitutions on the conformation of coat protein, once assembled. Each of the amino acid substitutions caused a change in the conformation as compared to wild-type coat protein, observed by at least one of the probes used. Thus, neither assembly nor expansion entirely corrected the conformational defects in the monomeric subunits of the folding mutants.
Capen
C M
CM
Department of Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut 06269-3125, USA.
Teschke
C M
CM
D019943:Amino Acid Substitution / Q000235:genetics*; D017100:Bacteriophage P22 / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D002152:Calorimetry, Differential Scanning; D002213:Capsid / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D006358:Hot Temperature; D011487:Protein Conformation; D011489:Protein Denaturation / Q000235:genetics; D017510:Protein Folding; D011498:Protein Precursors / Q000235:genetics / Q000378:metabolism; D017433:Protein Structure, Secondary / Q000235:genetics; D015678:Viral Structural Proteins / Q000235:genetics / Q000378:metabolism; D014771:Virion / Q000235:genetics / Q000502:physiology; D019065:Virus Assembly / Q000235:genetics*
D011498:Protein Precursors; D015678:Viral Structural Proteins; C111088:scaffolding protein, bacteriophage P22