A short repeat found in a small family of membrane-bound proteins. This repeat contains a conserved SPW motif in the first of two transmembrane helices.

1: New Knowledge from Old: In silico discovery of novel protein domains in Streptomyces coelicolor. Yeats C, Bentley S, Bateman A; BMC Microbiol 2003;3:3-3. PMID:12625841