Holin superfamily IV

The Holin superfamily IV is a group of integral membrane transport proteins. There are seven different holin superfamilies in total. The Holin superfamily IV includes the TC families:^[1]

• 1.E.10 - The Bacillus subtilis φ29 Holin (φ29 Holin) Family
• 1.E.16 - The Cph1 Holin (Cph1 Holin) Family
• 1.E.19 - The Clostridium difficile TcdE Holin (TcdE Holin) Family
• 1.E.40 - The Mycobacterial 4 TMS Phage Holin (MP4 Holin) Family

Superfamily IV includes four TC families, which includes members from Firmicutes, Actinobacteria and Fusobacteria. Their average sizes are (in amino acyl residues (aas)):

TC# 1.E.10 - 138 ± 6 aas

TC# 1.E.16 - 149 ± 15 aas

TC# 1.E.19 - 141 ± 12 aas

TC# 1.E.40 - 173 ± 149 aas

Thus, there is very little size variation among family members, except for family 40, which has members larger than the other proteins in this superfamily. All members of families 10 and 19 and many members of family 16 appear to have 3 transmembrane segments (TMSs), but some members of this last family are predicted to have 4 TMSs. The extra TMS in these proteins is at their N-termini.^[2]

See also

• Holin
• Lysin
• Transporter Classification Database

References

1. "Holin Superfamily IV". Transporter Classification Database. Retrieved 2016-03-20.
2. Reddy, Bhaskara L.; Saier Jr., Milton H. (2013-11-01). "Topological and phylogenetic analyses of bacterial holin families and superfamilies". Biochimica et Biophysica Acta (BBA) - Biomembranes 1828 (11): 2654–2671. doi:10.1016/j.bbamem.2013.07.004. PMC 3788059. PMID 23856191.