Accumulation of the Type IV prepilin triggers degradation of SecY and YidC and inhibits synthesis of Photosystem II proteins in the cyanobacterium Synechocystis PCC 6803

Abstract

SummaryType IV pilins are bacterial proteins that are small in size but have a broad range of functions, including motility, transformation competence and secretion. Although pilins vary in sequence, they possess a characteristic signal peptide that has to be removed by the prepilin peptidase PilD during pilin maturation. We generated a pilD (slr1120) null mutant of the cyanobacterium Synechocystis 6803 that accumulates an unprocessed form of the major pilin PilA1 (pPilA1) and its non-glycosylated derivative (NpPilA1). Notably, the pilD strain had aberrant membrane ultrastructure and did not grow photoautotrophically because the synthesis of Photosystem II subunits was abolished. However, other membrane components such as Photosystem I and ATP synthase were synthesized at levels comparable to the control strain. Proliferation of the pilD strain was rescued by elimination of the pilA1 gene, demonstrating that PilA1 prepilin inhibited the synthesis of Photosystem II. Furthermore, NpPilA1 co-immunoprecipitated with the SecY translocase and the YidC insertase, and both of these essential translocon components were degraded in the mutant. We propose that unprocessed prepilins inactivate an identical pool of translocons that function in the synthesis of both pilins and the core subunits of Photosystem II.

Ethylene Regulates the Physiology of the Cyanobacterium Synechocystis sp. PCC 6803 via an Ethylene Receptor

“…Our results mixing wildtype and SynEtr1DTM2 cells favor the idea that extracellular changes mediate the major effects of ethylene that we observed on phototaxis. It is unclear whether the changes in PSII levels are a primary or secondary effect of SynEtr1 signaling, because it has been observed previously that the accumulation of prepilin proteins can affect PSII levels by altering the translocation of proteins necessary for PSII formation (Linhartová et al, 2014). Thus, the alterations we see in PSII levels may be an indirect effect of this signaling system that is related to changes in pilin protein levels.…”

“…In both cases, proteins were separated by SDS-PAGE. PilA1 protein levels were analyzed with western blots using a 1:10,000 dilution of anti-PilA1 antibodies obtained from Dr. Roman Sobotka (Linhartová et al, 2014). A horseradish peroxidase-conjugated secondary antibody was used, and detection with luminol (Bio-Rad) was performed.…”

Identification of inner membrane translocase components of TolC‐mediated secretion in the cyanobacterium Synechocystis sp. PCC 6803

“…Peptide mass fingerprinting analysis of this band identified it as the pilin subunit PilA1 (Sll1694, data not shown), meaning that PilA1 in the exoproteome of Δ sll0141 , Δ sll0180 and Δ slr0369 presents a change in electrophoretic mobility. The Synechocystis pilin structural component PilA1 has been previously shown to be post‐translationally modified, including: (i) proteolytic cleavage (Linhartová et al ., ), (ii) methylation of the C‐terminus lysine (Kim et al ., ); and (iii) glycosylation (Kim et al ., ). We hypothesized that the difference in electrophoretic mobility could be due to changes in the glycosylation of PilA1.…”

Type 4 pili are dispensable for biofilm development in the cyanobacterium Synechococcus elongatus

“…Using PilFind (Imam et al ., ) for the prediction of T4P‐like signal peptides and their pre‐pilin peptidase methylation sites, we identified several pilA candidate genes: Synpcc7942_0048, Synpcc7942_0049, Synpcc7942_2479, Synpcc7942_2482, Synpcc7942_2484, Synpcc7942_2485, Synpcc7942_2590 and Synpcc7942_2591. These genes were previously reported by others as pilA candidates (Linhartova et al ., ). We examined the effect of inactivation of the pilA candidate genes on biofilm development.…”