The C-terminal domain of the bacteriophage T4 terminase docks on the prohead portal clip region during DNA packaging.
Bacteriophage ATP-based packaging motors translocate DNA into a pre-formed prohead through a dodecameric portal ring channel to high density. We investigated portal-terminase docking interactions at specifically localized residues within a terminase-interaction region (aa279-316) in the phage T4 portal protein gp20 equated to the clip domain of the SPP1 portal crystal structure by 3D modeling. Within this region, three residues allowed A to C mutations whereas three others did not, consistent with informatics analyses showing the tolerated residues are not strongly conserved evolutionarily. About 7.5nm was calculated by FCS-FRET studies employing maleimide Alexa488 dye labeled A316C proheads and gp17 CT-ReAsH supporting previous work docking the C-terminal end of the T4 terminase (gp17) closer to the N-terminal GFP-labeled portal (gp20) than the N-terminal end of the terminase. Such a terminase-portal orientation fits better to a proposed "DNA crunching" compression packaging motor and to portal determined DNA headful cutting.
Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, 108N. Greene St., Baltimore, MD 21201, USA.
Aparna Banerjee
AB
Dixit
Krishanu
K
Ray
Julie A
JA
Thomas
Lindsay W
LW
Black
D000595:Amino Acid Sequence; D017122:Bacteriophage T4 / Q000201:enzymology* / Q000502:physiology*; D036022:Capsid Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D019295:Computational Biology; D004252:DNA Mutational Analysis; D042003:DNA Packaging; D004706:Endodeoxyribonucleases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D056004:Molecular Dynamics Simulation; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011485:Protein Binding; D011487:Protein Conformation; D054730:Protein Interaction Domains and Motifs; D025941:Protein Interaction Mapping; D016415:Sequence Alignment
D036022:Capsid Proteins; C119911:portal protein, Bacteriophage T4; D004706:Endodeoxyribonucleases; C030894:terminase
Alexa 488; Alexa Fluor fluorescent dye; FCS-FRET; Fluorescence correlation spectroscopy-Förster resonance energy transfer; Phyre2; ReAsH; SDM; T4 portal clip region; T4 terminase; cold sensitive mutation; cs; site directed mutagenesis; specific tetra-cysteine peptide binding Fluorescein arsenical helix bis-EDT adduct; temperature sensitive mutation; ts