Self-assembles to form a helical, filamentous nucleocapsid (Probable) (PubMed:30135568). Together with capsid protein 2, wraps arounds the DNA and maintains it in an A-form (Probable) (PubMed:30135568). Capsid proteins probably maintain the DNA in A-form by non-specific desolvation and specific coordination of the DNA phosphate groups by positively charged residues (Probable) (PubMed:30135568). This certainly protects the viral DNA under conditions such as the extreme desiccation of its host (Probable). Heterodimer composed of major capsid protein VP4 and major capsid protein VP5. The N-terminus projects into a DNA groove.