Functional Domains of the P22 Scaffolding Protein

Although not strictly required for assembly proper, several minor proteins ultimately required for infectivity are incorporated during procapsid assembly. These are the portal protein and the ejection proteins 

However, whether the interaction is direct or indirect remains an open question. Although there is biochemical evidence suggesting a direct interaction of one pilot protein (gpl6) with the coat protein (Thomas and Prevelige, 1991), attempts to biochemically detect interactions between the scaffolding and the minor and portal proteins have met with failure (P. E. Prevelige, unpublished data). 

---