Maturation and processing of Spal, the lipoprotein involved in subtilin immunity in Bacillus subtilis ATCC 6633

Spal is a small lipoprotein that provides Bacillus subtilis with autoimmunity against the lantibiotic subtilin. We have investigated the maturation of Spal through the lipoprotein biosynthesis pathway, and analyzed the consequences of maturations in the acylation of the target lipobox in subtilin immunity. Further specificity of lipid acylation of the cysteine within the conserved sequence of the candidate lipobox (LSAC) was studied by site-directed mutagenesis. The mutants LSAA and LSCA blocked lipid attachment to the Spal protein. Cell-wall stress-sensing B. subtilis BSF 2470 was exploited to study the function of each mutant upon heterologous expression. This system allowed the monitoring of beta-galactosidase activity to the added subtilin at a sublethal dose. Mutants exhibited 2-fold reduction in beta-Gal activity, suggesting their contribution in subtilin autoimmunity. (C) 2009 Elsevier GmbH. All rights reserved.