Fluorescence and nucleic acid binding properties of the human T-cell leukemia virus-type 1 nucleocapsid protein.
We used intrinsic tryptophan fluorescence to study the nucleocapsid protein from human T-cell leukemia virus-type one, HTLV-1 p15, an 85-amino-acid protein with two Trp-containing zinc-finger motifs. Fluorescence spectra suggested an interaction between the two zinc fingers and another interaction involving the C-terminal tail and the zinc fingers. Titrations with nucleic acid revealed similar, sub-micromolar affinity for poly(dT) and poly(U) in 1 mM sodium phosphate, pH 7. Double-stranded DNA bound an order of magnitude weaker, suggesting helix-destabilizing activity. Base preference of p15 was T approximately U>I approximately C approximately G>A; affinity spanned about one order of magnitude. HTLV-1 p15 bound weaker and with less variation than reported values for either human or simian immunodeficiency virus homologues. The low affinity of p15 for nonspecific nucleic acids distinguishes it from other nucleocapsid proteins, and may suggest its involvement in additional steps of the virus life cycle other than RNA packaging.
Morcock
D R
DR
AIDS Vaccine Program, SAIC Frederick, National Cancer Institute - Frederick Cancer Research and Development Center, Bldg. 535, 4th floor, P.O. Box B, Frederick, MD 21702, USA.
Kane
B P
BP
Casas-Finet
J R
JR
D000595:Amino Acid Sequence; D015368:Human T-lymphotropic virus 1; D006863:Hydrogen-Ion Concentration; D015636:Magnesium Chloride; D008969:Molecular Sequence Data; D009696:Nucleic Acids / Q000737:chemistry*; D019590:Nucleocapsid Proteins / Q000737:chemistry* / Q000302:isolation & purification; D010710:Phosphates; D012191:Retroviridae Proteins / Q000737:chemistry*; D013050:Spectrometry, Fluorescence; D014364:Tryptophan / Q000737:chemistry; D016335:Zinc Fingers
D009696:Nucleic Acids; D019590:Nucleocapsid Proteins; D010710:Phosphates; D012191:Retroviridae Proteins; C489732:p15 protein, Human T-lymphotropic virus 1; D015636:Magnesium Chloride; D014364:Tryptophan; C018279:sodium phosphate