Protonation of individual histidine residues is not required for the pH-dependent entry of west nile virus: evaluation of the "histidine switch" hypothesis.
Histidine residues have been hypothesized to function as sensors of environmental pH that can trigger the activity of viral fusion proteins. We investigated a requirement for histidine residues in the envelope (E) protein of West Nile virus during pH-dependent entry into cells. Each histidine was individually replaced with a nonionizable amino acid and tested functionally. In each instance, mutants capable of orchestrating pH-dependent infection were identified. These results do not support a requirement for any single histidine as a pH-sensing "switch," and they suggest that additional features of the E protein are involved in triggering pH-dependent steps in the flavivirus life cycle.
Nelson
Steevenson
S
Viral Pathogenesis Section, Laboratory of Viral Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA.
Poddar
Subhajit
S
Lin
Tsai-Yu
TY
Pierson
Theodore C
TC
D019943:Amino Acid Substitution / Q000235:genetics; D002460:Cell Line; D017930:Genes, Reporter; D049452:Green Fluorescent Proteins; D006639:Histidine / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D017434:Protein Structure, Tertiary; D014759:Viral Envelope Proteins / Q000235:genetics / Q000378:metabolism*; D053586:Virus Internalization; D014902:West Nile virus / Q000502:physiology*
D014759:Viral Envelope Proteins; D049452:Green Fluorescent Proteins; D006639:Histidine