Protein translocation and thylakoid biogenesis in cyanobacteria

Abstract

Cyanobacteria exhibit a complex form of membrane differentiation that sets them apart from most bacteria. Many processes take place in the plasma membrane, but photosynthetic light capture, electron transport and ATP synthesis take place in an abundant internal thylakoid membrane. This review considers how this system of subcellular compartmentalisation is maintained, and how proteins are directed towards the various subcompartments--specifically the plasma membrane, periplasm, thylakoid membrane and thylakoid lumen. The involvement of Sec-, Tat- and signal recognition particle- (SRP)-dependent protein targeting pathways is discussed, together with the possible involvement of a so-called 'spontaneous' pathway for the insertion of membrane proteins, previously characterised for chloroplast thylakoid membrane proteins. An intriguing aspect of cyanobacterial cell biology is that most contain only a single set of genes encoding Sec, Tat and SRP components, yet the proteomes of the plasma and thylakoid membranes are very different. The implications for protein sorting mechanisms are considered. This article is part of a Special Issue entitled Organization and dynamics of bioenergetic systems in bacteria, edited by Prof Conrad Mullineaux.

Evidence supporting an antimicrobial origin of targeting peptides to endosymbiotic organelles

“…We also considered a set of peptides, hereafter referred to as secretory signal peptides (SPs), which function as address tags just as TPs do, but targeting a different set of subcellular destinations. SPs have a well-established evolutionary link and all use Sec-type translocation systems (von Heijne 1990;Frain et al 2016;Schatz and Dobberstein 1996). For this study, we consider the following peptides as belonging to the SP group: bacterial SPs (bSPs) that target proteins for secretion into their periplasm, their eukaryotic relatives (eSPs) that target cytosolic proteins to the endoplasmic reticulum, and (tSPs), more commonly referred to as thylakoid targeting peptides, that enable proteins to be targeted from the chloroplast stroma to the thylakoids (von Heijne et al 1989;Schatz and Dobberstein 1996).…”

Engineering Cyanobacterial Cell Morphology for Enhanced Recovery and Processing of Biomass

“…Additionally, morphology engineering may have useful applications for increasing the resistance of cyanobacteria to grazing species that frequently contaminate open-air ponds and which have preferences for bacteria with specific dimensions due to physical feeding constraints (e.g., size of mouth/digestive tract) (37)(38)(39). Finally, a methodology for gentle cell lysis of cyanobacteria might enable the recovery of sensitive complexes or structures that can be destroyed under harsh conditions used routinely for cyanobacterial lysis (40).…”

Cellular compartmentation follows rules: The Schnepf theorem, its consequences and exceptions

“…[36]) or, as e.g. in case of cyanobacterial thylakoids [37], by a regular biological membrane. Thylakoids are internal membrane structures consisting of a lipid bilayer, in which the photosynthetic apparatus of cyanobacteria is embedded: they surround a non-plasmatic phasethe thylakoid lumen [38].…”

“…Thylakoids are internal membrane structures consisting of a lipid bilayer, in which the photosynthetic apparatus of cyanobacteria is embedded: they surround a non-plasmatic phasethe thylakoid lumen [38]. So far it is discussed whether thylakoid membranes are actually fused to the cyanobacterial plasma membrane or whether thylakoids exist as a detached internal compartment [37,38]. It is thus unclear whether the Schnepf theorem can be applied to the cyanobacterial thylakoids.…”