1.C.70 The Streptococcal Pore-forming CAMP Factor (CAMP-F) Family

Streptococcus pyogenes, S. agalastiae, S. uberis and S. canis contain related pore-forming toxins called CAMP factors. They are about 255 aas long and have a single N-terminal TMS. The S. pyogenes and S. agalactiae homologues are 60% identical. CAMP factors are hemolytic and form discrete transmembrane oligomeric pores with diameters of about 1.6 nm. Electron microscopy reveals circular membrane lesions of heterogeneous sizes, up to 12-15 nm in diameter (Lang and Palmer, 2003).   The toxin allows the passive diffusion of small molecules across the membrane. Toxic activity depends on the presence of sphingomyelin (50%, 20% and 19% in sheep, human and rabbit red blood cells, respectively).

The structure of this toxin has been determined, revealing a structural fold composed of 5 + 3-helix bundles. The N-terminal 5-helix bundle is responsible for membrane permeabilization, whereas the C-terminal 3-helix bundle is likely responsible for host receptor binding. The C-terminal domain inhibited the activity of both full-length toxin and its N-terminal domain. The linker region is highly conserved and has a conserved DLXXXDXAT sequence motif. This linker region  interacted with both terminal CAMP factor domains, and mutagenesis disclosed that the conserved sequence motif is required for CAMP factor's co-hemolytic activity (Jin et al. 2018).





Jin, T., E. Brefo-Mensah, W. Fan, W. Zeng, Y. Li, Y. Zhang, and M. Palmer. (2018). Crystal structure of the CAMP factor provides insights into its membrane-permeabilizing activity. J. Biol. Chem. 293: 11867-11877.

Lang, S. and M. Palmer. (2003). Characterization of Streptococcus agalactiae CAMP factor as a pore-forming toxin. J. Biol. Chem. 278: 38167-38173.

Zafar, A., M. Stone, S. Ibrahim, Z. Parveen, Z. Hasan, E. Khan, R. Hasan, J. Wain, and K. Bamford. (2011). Prevalent genotypes of meticillin-resistant Staphylococcus aureus: report from Pakistan. J. Med. Microbiol. 60: 56-62.


TC#NameOrganismal TypeExample

Pore-forming CAMP factor of 255 aas.  The 3-d structure is known (Zafar et al. 2011).  See description of the structure  in the family description.


CAMP factor of Streptococcus agalactiae (CAD47659)


Pore-forming CAMP factor of 257 aas.

CAMP factor of Streptococcus pyogenes


Uncharacterized protein of 415 aas

UP of Anaerococcus sp. SB3


Uncharacterized protein of 459 aas

UP of Finegoldia magna


Uncharacterized protein of 392 aas and 1 N-terminal TMS.

UP of Peptoniphilus phoceensis


TC#NameOrganismal TypeExample