title: The Anabaena sp. PCC 7120 Exoproteome: Taking a Peek outside the Box.
abstract: The interest in examining the subset of proteins present in the extracellular milieu, the exoproteome, has been growing due to novel insights highlighting their role on extracellular matrix organization and biofilm formation, but also on homeostasis and development. The cyanobacterial exoproteome is poorly studied, and the role of cyanobacterial exoproteins on cell wall biogenesis, morphology and even physiology is largely unknown. Here, we present a comprehensive examination of the Anabaena sp. PCC 7120 exoproteome under various growth conditions. Altogether, 139 proteins belonging to 16 different functional categories have been identified. A large fraction (48%) of the identified proteins is classified as "hypothetical", falls into the "other categories" set or presents no similarity to other proteins. The evidence presented here shows that Anabaena sp. PCC 7120 is capable of outer membrane vesicle formation and that these vesicles are likely to contribute to the exoproteome profile. Furthermore, the activity of selected exoproteins associated with oxidative stress has been assessed, suggesting their involvement in redox homeostasis mechanisms in the extracellular space. Finally, we discuss our results in light of other cyanobacterial exoproteome studies and focus on the potential of exploring cyanobacteria as cell factories to produce and secrete selected proteins.
authors.affiliation: Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto 4150-180, Portugal. paulo.oliveira@ibmc.up.pt.|IBMC-Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto 4150-180, Portugal. paulo.oliveira@ibmc.up.pt.
authors.forename: Paulo
authors.initials: P
authors.lastname: Oliveira
authors.affiliation: Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto 4150-180, Portugal. nderesen@ulb.ac.be.|IBMC-Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto 4150-180, Portugal. nderesen@ulb.ac.be.|Laboratoire du Biologie du Noyau, Institut de Biologie & de Médecine Moléculaire, Université Libre de Bruxelles, Charleroi B-6041, Belgium. nderesen@ulb.ac.be.
authors.forename: Nuno M
authors.initials: NM
authors.lastname: Martins
authors.affiliation: Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto 4150-180, Portugal. marina.santos@ibmc.up.pt.|IBMC-Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto 4150-180, Portugal. marina.santos@ibmc.up.pt.
authors.forename: Marina
authors.initials: M
authors.lastname: Santos
authors.affiliation: ChELSI Institute, Chemical and Biological Engineering, University of Sheffield, Sheffield S1 3JD, UK. n.couto@sheffield.ac.uk.
authors.forename: Narciso A S
authors.initials: NA
authors.lastname: Couto
authors.affiliation: ChELSI Institute, Chemical and Biological Engineering, University of Sheffield, Sheffield S1 3JD, UK. p.c.wright@sheffield.ac.uk.
authors.forename: Phillip C
authors.initials: PC
authors.lastname: Wright
authors.affiliation: Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto 4150-180, Portugal. pmtamagn@ibmc.up.pt.|IBMC-Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto 4150-180, Portugal. pmtamagn@ibmc.up.pt.|Faculdade de Ciências, Departamento de Biologia, Universidade do Porto, Porto 4169-007, Portugal. pmtamagn@ibmc.up.pt.
authors.forename: Paula
authors.initials: P
authors.lastname: Tamagnini