TABLE 1.

Structure and function of major outer membrane proteins of A. baumannii.

Name of porin	Molecular weight	Structure	Proposed role in A. baumannii	References
OmpA	28–36 kDa	Eight-stranded Beta barrel shaped	Cytotoxic protein. Mediates attachment to host cells via fibronectin.	Choi et al., 2005; Smani et al., 2012; Confer and Ayalew, 2013
CarO	25/29 kDa	Eight-stranded beta barrel shaped	Uptake of glycine and ornithine. Also implicated in carbapenem resistance.	Limansky et al., 2002; Siroy et al., 2005; Zahn et al., 2015; Zhu et al., 2019
OprD/OccAB1	43 kDa	Eighteen-stranded beta-barrel shaped	Allows diffusion of basic amino acids and beta-lactam class of antibiotics into the cell.	Dupont et al., 2005; Zahn et al., 2016
Omp33-36	33–36 kDa	Yet to be studied	Implicated in imipenem resistance. Induces apoptosis in host cells by activating caspases 3 and 9.	Clark, 1996; Rumbo et al., 2014
AbuO	50.2 kDa (Theoretical)	Three domains—four-stranded beta barrel, α-helical barrel and α- β mixed barrel	Homolog of E. coli TolC protein. Involved in pH and bile salt tolerance.	Srinivasan et al., 2015
DcaP	47–50 kDa	Sixteen-stranded beta-barrel shaped	An Omp with preference for anionic compounds. Involved in transport of phthalates into the cell.	Bhamidimarri et al., 2019
OmpW	Yet to be studied	Eight-stranded beta-barrel shaped. (Theoretical)	Serves as a colistin binding site. Facilitates iron uptake into the cell.	Catel-Ferreira et al., 2016