Domains in lambda Cro repressor. A calorimetric study.
Thermodynamic properties of a mutant lambda Cro repressor with Cys replacing Val55 were studied calorimetrically. Formation of the S-S cross-link between neighboring Cys55 residues in this dimeric molecule leads to stabilization of a structure formed by the C-terminal parts of the two polypeptide chains, which behave as a single cooperative domain upon protein denaturation by heating. This composite domain is very stable at neutral pH and disrupts at 110 degrees C. The S-S-cross-linked tryptic fragment (residues 22-66), which includes this C-terminal domain, has similar stability. The N-terminal parts of the polypeptide chains do not form any stable structure when isolated, but in S-S-cross-linked dimer, they form a single cooperative block which melts in an all-or-none way 9 degrees C higher than the un-cross-linked protein. The observed cooperation of the distant N-terminal parts in dimer raises questions regarding lambda Cro repressor structure in solution.
Griko
Y V
YV
Department of Biology, Johns Hopkins University, Baltimore, Maryland 21218.
Rogov
V V
VV
Privalov
P L
PL
D002151:Calorimetry; D004268:DNA-Binding Proteins; D004591:Electrophoresis, Polyacrylamide Gel; D008958:Models, Molecular; D012097:Repressor Proteins / Q000737:chemistry*; D013816:Thermodynamics; D014157:Transcription Factors / Q000737:chemistry*; D014764:Viral Proteins; D054334:Viral Regulatory and Accessory Proteins; D014961:X-Ray Diffraction
D004268:DNA-Binding Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; D014764:Viral Proteins; D054334:Viral Regulatory and Accessory Proteins; C016649:phage repressor proteins