Heptad repeat 2 in herpes simplex virus 1 gH interacts with heptad repeat 1 and is critical for virus entry and fusion.
Herpes simplex virus 1 (HSV-1) entry into cells and cell-cell fusion mediated by HSV-1 glycoproteins require four glycoproteins, gD, gB, gH, gL. Of these, gH is the only one that so far exhibits structural-functional features typical of viral fusion glycoproteins, i.e., a candidate fusion peptide and, downstream of it, a heptad repeat (HR) segment able to form a coiled coil, named HR-1. Here, we show that gH carries a functional HR-2 capable of physical interaction with HR-1. Specifically, mutational analysis of gH aimed at increasing or decreasing the ability of HR-2 to form a coiled coil resulted in an increase or decrease of fusion activity, respectively. HSV infection was modified accordingly. A mimetic peptide with the HR-2 sequence inhibited HSV-1 infection in a specific and dose-dependent manner. Circular dichroism spectroscopy showed that both HR-2 and HR-1 mimetic peptides adopt mainly random conformation in aqueous solution, while a decrease in peptide environmental polarity determines a conformational change, with a significant increase of the alpha-helical conformation content, in particular, for the HR-1 peptide. Furthermore, HR-1 and HR-2 mimetic peptides formed a stable complex, as revealed in nondenaturing electrophoresis and by circular dichroism. The mixture of HR-1 and HR-2 peptides reversed the inhibition of HSV infection exerted by the single peptides. Complex formation between HR-1 and HR-2 was independent of the presence of adjacent gH sequences and of additional glycoproteins involved in entry and fusion. Altogether, HR-2 adds to the features typical of class 1 fusion glycoproteins exhibited by HSV-1 gH.
Department of Experimental Pathology, Section on Microbiology and Virology, University of Bologna, Italy.
Tatiana
T
Gianni
Angela
A
Piccoli
Carlo
C
Bertucci
Gabriella
G
Campadelli-Fiume
D020816:Amino Acid Motifs; D000818:Animals; D000954:Antigens, Surface / Q000032:analysis; D000998:Antiviral Agents / Q000494:pharmacology; D002460:Cell Line; D002942:Circular Dichroism; D006224:Cricetinae; D004252:DNA Mutational Analysis; D017930:Genes, Reporter; D018259:Herpesvirus 1, Human / Q000235:genetics / Q000502:physiology*; D008561:Membrane Fusion; D008968:Molecular Conformation; D018716:Molecular Mimicry; D010455:Peptides / Q000494:pharmacology; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D014759:Viral Envelope Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D001616:beta-Galactosidase / Q000032:analysis / Q000235:genetics
D000954:Antigens, Surface; D000998:Antiviral Agents; D010455:Peptides; D014759:Viral Envelope Proteins; C044200:glycoprotein H, herpes simplex virus type 1; D001616:beta-Galactosidase