This bacterial family of proteins contains phage tail tube proteins related to the Mu phage protein Swiss:P79679 [1]. Bacteriophage Mu has an eicosahedral head and contractile tail. The tail is composed of an outer sheath and an inner tube.

1: Discovery of the tail tube gene of bacteriophage Mu and sequence analysis of the sheath and tube genes. Takeda S, Sasaki T, Ritani A, Howe MM, Arisaka F; Biochim Biophys Acta 1998;1399:88-92. PMID:9714755