1.C.67 The SphH Hemolysin (SphH) Family

The Leptospira interrogans hemolysin, SphH, also called sphingomyelinase C precursor, does not hydrolyze phospholipids or sphingomyelin although homologues do (Lee et al., 2002). Instead, it exhibits hemolysis activity on erythrocytes and forms pores in several mammalian cell types, accounting in part for its toxic activity (Lee et al., 2002). Morphological pore-like structures in the membranes of sheep erythrocytes could be seen by transmission electron microscopy (Lee et al., 2002).

SphH is 554 aas in length and exhibits a single hydrophobic TMS at its N-terminus, probably a cleavable leader sequence. Otherwise it is a hydrophilic protein. It is homologous to a variety of sphingomyelinases, phospholipases and β-hemolysins (β-toxins) from a wide range of Gram-negative and Gram-positive bacteria. Distant homologues are also present in eukaryotes.

The transport reaction catalyzed by pore-forming SphH is:

large and small molecules (in) molecules (out)