Analysis of the novel mouse WAP motif proteins ELM1 and ELM2 and their human homologs

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Antibacterial proteins are important participants in the innate immunity system. Elafin and SLPI are the WAP motif proteins with both antibacterial activity and antiprotease activity, and their role in innate immunity is under intense investigation. We cloned two novel antibacterial WAP motif proteins from mice, SWAM1 and SWAM2. SWAM1 and SWAM2 are composed of a signal sequence and a single WAP motif that has high homologies with that of elafin and SLPI. SWAM1 is constitutively expressed in kidney, and epididymis, and is induced in the pneumonic lung. SWAM2 is constitutively expressed in tongue. SWAM1 and SWAM2 inhibit the growth of both Escherichia coli and Staphylococcus aureus at an 1C90 of 10 υM. Human genes LOC149709 and huWAP2 are considered to be human SWAM1 and SWAM2, respectively. These and several VAP motif proteins (WAP1, elafin, SLPI, HE4, eppin, C20orf170, LOC164237, and WFDC3) form a gene cluster on human chromosome 20, suggesting that they may be derived from the same ancestral gene by gene duplication. Our results underscore the role of the WAP motif as a skeletal motif to form antibacterial proteins, and warrant the study of antibacterial activity in other WAP motif proteins.