A microcin processing peptidase‐like protein of the cyanobacterium Synechococcus elongatus is essential for secretion of biofilm‐promoting proteins

• Published in: Environmental microbiology reports Vol. 11; no. 3; pp. 456 - 463
• Main Authors: Parnasa, Rami, Sendersky, Eleonora, Simkovsky, Ryan, Waldman Ben‐Asher, Hiba, Golden, Susan S., Schwarz, Rakefet
• Format: Journal Article
• Language: English
• Published: Hoboken, USA John Wiley & Sons, Inc 01.06.2019
• Subjects: Amino Acid Motifs; Bacterial Proteins - metabolism; Bacteriocins - chemistry; Bacteriocins - genetics; Bacteriocins - metabolism; Biofilms; Biofilms - growth & development; Cell membranes; Cyanobacteria; Deactivation; Extracellular Space - metabolism; Genes; Genomic analysis; Glycine; Inactivation; Maturation; Mutants; Mutation; Peptidase; Peptidases; Peptide Hydrolases - chemistry; Peptide Hydrolases - genetics; Peptide Hydrolases - metabolism; Peptides; Periplasmic space; Protein Processing, Post-Translational; Protein Transport; Proteins; Proteome; Scanning electron microscopy; Secretion; Synechococcus - chemistry; Synechococcus - genetics; Synechococcus - metabolism; Synechococcus - physiology; Synechococcus elongatus
• ISSN: 1758-2229; 1758-2229
• DOI: 10.1111/1758-2229.12751

Summary Small secreted compounds, e.g. microcins, are characterized by a double‐glycine (GG) secretion motif that is cleaved off upon maturation. Genomic analysis suggests that small proteins that possess a GG motif are widespread in cyanobacteria; however, the roles of these proteins are largely unknown. Using a biofilm‐proficient mutant of the cyanobacterium Synechococcus elongatus PCC 7942 in which the constitutive biofilm self‐suppression mechanism is inactivated, we previously demonstrated that four small proteins, Enable biofilm formation with a GG motif (EbfG1‐4), each with a GG motif, enable biofilm formation. Furthermore, a peptidase belonging to the C39 family, Peptidase transporter enabling Biofilm (PteB), is required for secretion of these proteins. Here, we show that the microcin processing peptidase‐like protein encoded by gene Synpcc7942_1127 is also required for biofilm development – inactivation of this gene in the biofilm‐proficient mutant abrogates biofilm development. Additionally, this peptidase‐like protein (denoted EbfE – enables biofilm formation peptidase) is required for secretion of the EbfG biofilm‐promoting small proteins. Given their protein‐domain characteristics, we suggest that PteB and EbfE take part in a maturation‐secretion system, with PteB being located to the cell membrane while EbfE is directed to the periplasmic space via its secretion signal.