Corynebacterium jeikeium jk0268 Constitutes for the 40 Amino Acid Long PorACj, Which Forms a Homooligomeric and Anion-Selective Cell Wall Channel

Abstract

Corynebacterium jeikeium, a resident of human skin, is often associated with multidrug resistant nosocomial infections in immunodepressed patients. C. jeikeium K411 belongs to mycolic acid-containing actinomycetes, the mycolata and contains a channel-forming protein as judged from reconstitution experiments with artificial lipid bilayer experiments. The channel-forming protein was present in detergent treated cell walls and in extracts of whole cells using organic solvents. A gene coding for a 40 amino acid long polypeptide possibly responsible for the pore-forming activity was identified in the known genome of C. jeikeium by its similar chromosomal localization to known porH and porA genes of other Corynebacterium strains. The gene jk0268 was expressed in a porin deficient Corynebacterium glutamicum strain. For purification temporarily histidine-tailed or with a GST-tag at the N-terminus, the homogeneous protein caused channel-forming activity with an average conductance of 1.25 nS in 1M KCl identical to the channels formed by the detergent extracts. Zero-current membrane potential measurements of the voltage dependent channel implied selectivity for anions. This preference is according to single-channel analysis caused by some excess of cationic charges located in the channel lumen formed by oligomeric alpha-helical wheels. The channel has a suggested diameter of 1.4 nm as judged from the permeability of different sized hydrated anions using the Renkin correction factor. Surprisingly, the genome of C. jeikeium contained only one gene coding for a cell wall channel of the PorA/PorH type found in other Corynebacterium species. The possible evolutionary relationship between the heterooligomeric channels formed by certain Corynebacterium strains and the homooligomeric pore of C. jeikeium is discussed.

Identification and characterization of a cell wall porin from <i>Gordonia jacobaea</i>

“…5) having one side highly hydrophobic and another side hydrophilic and charged. This organization is presumably sufficient for the stabilization and anchorage in the mycolic acid layer as has been observed in PorH from C. efficiens, PorA from C. callunae and PorACj from C. jeikeium (Abdali et al, 2013;Hünten et al, 2005a, b).…”

“…However, there are some microbial pore-forming proteins where a-helix structures are relevant for their stability, such as PorH from Corynebacterium glutamicum, C. efficiens, C. callunae and PorACj from C. jeikeium (Abdali et al, 2013;Hünten et al, 2005a, b). Other proteins, like PorA from M. tuberculosis, have an N-terminal domain with both a-helix and b-sheet secondary structures (Teriete et al, 2010;Yang et al, 2011).…”

Discovery of a cell wall porin in the mycolic‐acid‐containing actinomycete Dietzia marisDSM 43672

“…However, some exhibit cation selectivity (as in D. maris) whereas others are anion-selective, although it is likely that each organism will possess channels with both types of selectivity in order to facilitate uptake of the full range of hydrophilic solutes. More interestingly, some porins appear to work as hetero-oligomers [18,46] whereas others form likely homo-oligomers [47].…”

Identification and characterization of smallest pore-forming protein in the cell wall of pathogenic Corynebacterium urealyticum DSM 7109

“…In the closely related Corynebacterium species C. glutamicum and C. efficiens , porA and porH genes encode for PorA and PorH proteins, which assemble for large, water-filled cell wall pores [ 27 – 30 ]. We could also previously demonstrate that a channel-forming protein, named PorACj, was identified in the known genome of C. jeikeium by the similar chromosomal localization of its gene to the known porH and porA genes of other Corynebacterium strains [ 31 ]. However, in contrast to certain Corynebacterium species, where two polypeptides PorA and PorH are needed to form a functional cell wall pore, the pore in the cell wall of C. jekeium is formed by a single polypeptide PorACj [ 31 ].…”

“…In all other cases, the genes are located in tandem between the genes coding for the chaperone GroEL2 and the polyphosphate kinase PKK2 [ 30 ]. So far, we demonstrated that PorACj is the smallest polypeptide forming well defined and stable channels [ 31 ]. The complete genome sequence of C. urealyticum DSM 7109 is known [ 13 ].…”