1.M.5.  The Putative Spanin5 (Spanin5) Family 

This family initially consisted of a single pair of proteins, both designated 'spanin' in the NCBI and UniProt databases, and both having an N-terminal TMS. They are from Burkholderia phage BcepF1 and are encoded by adjacent genes.  More homoogues have since been discovered, and some are included in TCDB.  They probably all consist of two proteins, one about 100 - 110 aas long, and the other of about 60 aas, also with one N-terminal TMS.