From the SEA Faculty at the 2023 Faculty meeting:

In many DN phages, the gene found between the portal and scaffolding protein should be called a capsid maturation protease. Historically, this gene has been called a MuF-like minor capsid protein, which as described in the approved function list can no longer be called. When you run HHPRED, you will likely find hits to MuF, but not hits to proteases. However, many of these genes have hits that have high similarity and probability to gp15 in D29 in Uniprot (Hit O6420smile. This can be done by selecting Uniprot as one of your algorithms in HHPRED. Because we know gp15 in D29 is a capsid maturation protease, having a strong hit to this protein allows you to call this a capsid maturation protease.