Secondary structure switching in Cro protein evolution.
We report the solution structure of the Cro protein from bacteriophage P22. Comparisons of its sequence and structure to those of lambda Cro strongly suggest an alpha-to-beta secondary structure switching event during Cro evolution. The folds of P22 Cro and lambda Cro share a three alpha helix fragment comprising the N-terminal half of the domain. However, P22 Cro's C terminus folds as two helices, while lambda Cro's folds as a beta hairpin. The all-alpha fold found for P22 Cro appears to be ancestral, since it also occurs in cI proteins, which are anciently duplicated paralogues of Cro. PSI-BLAST and transitive homology analyses strongly suggest that the sequences of P22 Cro and lambda Cro are globally homologous despite encoding different folds. The alpha+beta fold of lambda Cro therefore likely evolved from its all-alpha ancestor by homologous secondary structure switching, rather than by nonhomologous replacement of both sequence and structure.
Newlove
Tracey
T
Department of Biochemistry and Molecular Biophysics, University of Arizona, Tucson, AZ 85701 USA.
Konieczka
Jay H
JH
Cordes
Matthew H J
MH
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D010582:Bacteriophage lambda / Q000737:chemistry* / Q000235:genetics; D002942:Circular Dichroism; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics; D019143:Evolution, Molecular; D008969:Molecular Sequence Data; D017433:Protein Structure, Secondary; D012097:Repressor Proteins / Q000737:chemistry* / Q000235:genetics; D017385:Sequence Homology; D014764:Viral Proteins / Q000737:chemistry* / Q000235:genetics; D054334:Viral Regulatory and Accessory Proteins
D004268:DNA-Binding Proteins; D012097:Repressor Proteins; D014764:Viral Proteins; D054334:Viral Regulatory and Accessory Proteins; C016649:phage repressor proteins