Stably accumulated precursor of SapB (PubMed:22486809). Lanthionine-containing peptide devoid of antibiotic properties (PubMed:15277670). A surface active peptide involved in the efficient formation of aerial mycelium when cells are grown in rich media. Has an overlapping function with the surface-active chaplin proteins; chaplins are essential on minimal medium while on rich medium both chaplins and SapB are required for efficient aerial hyphae formation (PubMed:17462011). Required under conditions of high osmolarity where it may change the physical properties of the chaplin layer to allow hyphae to grow into air (Probable). Suggested to self-assemble at air-water interfaces, thus providing a film of surfactant through which nascent aerial hyphae can emerge; the aerial hyphae differentiate further into spores (PubMed:2032288). Application to bald mutants (bld, unable to make aerial hyphae) restores hyphae growth (PubMed:2032288, PubMed:9822824). Application to chaplin negative mutants as well as ramC-ramS-ramA-ramB and ramR deletions also restores aerial hyphae growth and sporulation (PubMed:17462011). Reduces surface tension of water from 72 to 30 mJ/m(2) (PubMed:9822824). RamS precursor protein (detected by an anti-propeptide antibody and by a C-terminal His-tag) is associated with the cell membrane in a non ramR-dependent fashion (PubMed:22486809). Present in a zone around colonies undergoing aerial hyphae formation and around spores (PubMed:2032288). Expression levels are media-dependent; well expressed in spores grown on rich R5, about 4-fold less on rich MS and less again on minimal mannitol media. Secreted in rich R5 but not in minimal mannitol media (PubMed:22309453). Starts to be expressed as aerial mycelium forms on rich solid medium after 3 days growth and in spores; only forms during growth on solid medium (PubMed:2450872, PubMed:2032288). Strongly expressed in spores (PubMed:2450872, PubMed:9822824). Most strongly expressed in spores from rich R5 media, less well in rich MS and even less well on minimal mannitol media (at protein level) (PubMed:22309453). The RamS precursor protein (detected by an anti-propeptide antibody and by a C-terminal His-tag) is detected from at least 16 hours post-germination on both rich and minimal media and is detected for at least 52 hours (at protein level) (PubMed:22486809). The mature lanthionine-containing peptide SapB is expressed by 3 days growth on rich medium, expression increases slightly over 7 days (at protein level). Expression requires ramR, not expressed in minimal medium (at protein level) (PubMed:12453210). Not synthesized in bld mutants (blocked in aerial hyphae formation), synthesized in whi mutants (spore formation is prevented) (at protein level) (PubMed:2032288). SapB is expressed on rich but not minimal medium (at protein level) (PubMed:2032288, PubMed:17462011). However it is expressed after 6 days growth on minimal medium in a chaplin-negative strain (at protein level) (PubMed:17462011). Induced by growth on osmolytes; slight induction by 10% sucrose, more strongly induced by 0.5 M KCl (at protein level) (PubMed:22309453). Probably part of the ramC-ramS-ramA-ramB operon (PubMed:12100547, PubMed:12453210). Also has its own, ramR-independent promoter. On both rich and minimal medium transcription is constitutive, rising to a plateau about 24 hours post-germination on all media; unaffected by ramR disruption (PubMed:22486809). Maturation involves the enzymatic conversion of Ser into dehydrated AA and the formation of thioether bonds with cysteine, probably by RamC (PubMed:15277670). This is followed by membrane translocation and cleavage of the modified precursor (Probable). The RamS precursor protein (detected by an anti-propeptide antibody and by a C-terminal His-tag) is detected from at least 16 hours post-germination; its apparent molecular weight decreases starting from about 34 hours, when its probable modifying enzyme ramC is transcribed. Surfactin, a B.subtilis cyclic lipopeptide antibiotic which prevents aerial hyphae formation in S.coelicolor, decreases localization of RamS precursor protein to the cell membrane, suggesting that processing only occurs at the cell membrane (PubMed:22486809). On rich R5 medium. On rich MS medium. Single deletion of ramS leads to a severe delay in aerial hyphae growth (PubMed:12453210). Deletion of the ramC-ramS-ramA-ramB operon on rich medium leads to an initially bald (no aerial hyphae) phenotype; after 4 days develops a substantial aerial mycelium. Wild-type mycelium on minimal medium (PubMed:17462011, PubMed:22309453). No expression of SapB, normal expression of chaplins. A complete chaplin-negative plus ram-negative strain (deletion of ramR or the ramC-ramS-ramA-ramB operon) leads to the complete loss of robust aerial hyphae (PubMed:17462011). Belongs to the lanthionine-containing morphogen family.