Phage like it HOT: solution structure of the bacteriophage P1-encoded HOT protein, a homolog of the theta subunit of E. coli DNA polymerase III.
DNA polymerase III, the main replicative polymerase of E. coli, contains a small subunit, theta, that binds to the epsilon proofreading subunit and appears to enhance the enzyme's proofreading function--especially under extreme conditions. It was recently discovered that E. coli bacteriophage P1 encodes a theta homolog, named HOT. The (1)H-(15)N HSQC spectrum of HOT exhibits more uniform intensities and less evidence of conformational exchange than that of theta; this uniformity facilitates a determination of the HOT solution structure by NMR. The structure contains three alpha helices, as reported previously for theta; however, the folding topology of the two proteins is very different. Residual dipolar coupling measurements on labeled theta support the conclusion that it is structurally homologous with HOT. As judged by CD measurements, the melting temperature of HOT was 62 degrees C, compared to 56 degrees C for theta, consistent with other data suggesting greater thermal stability of the HOT protein.
Derose
Eugene F
EF
Laboratory of Structural Biology, NIEHS, Box 12233, Research Triangle Park, NC 27709, USA.
Kirby
Thomas W
TW
Mueller
Geoffrey A
GA
Chikova
Anna K
AK
Schaaper
Roel M
RM
London
Robert E
RE
D000595:Amino Acid Sequence; D017101:Bacteriophage P1 / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics; D002942:Circular Dichroism; D004258:DNA Polymerase III / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000737:chemistry / Q000201:enzymology / Q000235:genetics; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D013816:Thermodynamics; D014764:Viral Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
D014764:Viral Proteins; C500758:HOT protein, bacteriophage P1; D004258:DNA Polymerase III