Structural parameters of the Pf1 gene 5 protein-DNA complex in solution by neutron scattering.
Neutron-scattering experiments have been performed on the intracellular complex formed by the gene 5 protein and single-stranded DNA in cells infected by filamentous bacteriophage Pf1. The contrast matched point of the complex (37% 2H2O) is lower than expected and implies that a substantial fraction of potentially labile hydrogen atoms are unable to exchange with the solvent. The mass/length ratio of the complex (3270 daltons/A) indicates an axial subunit repeat of 5.1 A, a value much larger than the subunit repeat previously determined in fibres. The measured value of the cross-sectional radius of gyration at infinite contrast (Rc = 43.3 A) indicates an outer radius of 60 to 63 A for the complex. The variation in Rc with contrast shows that regions of higher scattering density are located, on average, towards the outside of the complex. The high-angle region of the intensity curve (measured in 2H2O) reveals a clear subsidiary maximum at 0.105 A-1 arising from the 60 A helical pitch of the nucleoprotein complex. The structural parameters of the Pf1 gene 5 protein-DNA complex in solution are compared with those of the fd gene 5 protein-DNA complex.
Biophysics Laboratories, Portsmouth Polytechnic, U.K.
G G
GG
Kneale
S E
SE
Plyte
P
P
Timmins
D001435:Bacteriophages / Q000235:genetics; D004247:DNA / Q000737:chemistry* / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D009502:Neutrons; D012542:Scattering, Radiation; D012996:Solutions; D014764:Viral Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D014961:X-Ray Diffraction
D004268:DNA-Binding Proteins; D012996:Solutions; D014764:Viral Proteins; C067863:gene 5 protein, Pseudomonas phage Pf1; D004247:DNA