1.B.58 The Nocardial Hetero-oligomeric Cell Wall Channel (NfpA/B) Family
The cell wall outer membrane of Nocardia farcinica contains a cation-selective cell wall channel, which may be responsible for the limited permeability of the cell wall of N. farcinica to negatively charged antibiotics. Based on partial sequencing of the protein responsible for channel formation derived from N. farcinica ATTC 3318, Klackta et al. (2010) were able to identify the corresponding genes (nfa15890 and nfa15900) within the known genome of N. farcinica IFM 10152. The corresponding genes of N. farcinica ATTC 3318 were separately expressed in Escherichia coli and purified to homogeneity. The proteins were designated NfpA and NfpB, for N. farcinica porin A and B. The proteins together (but not alone) could form channels in lipid bilayer membranes.
The generalized reactin catalyzed by the NfpA/NfpB complex is:
small molecules (out) %u21CC small molecules (in).
The heteromeric porin, NfpA/NfpB (Kläckta et al., 2010). Sugars, amino acids and antibiotics are transported. The cation selective N. farcinica channel exhibits strong interactions with the positively charged antibiotics; amikacin and kanamycin, and the negatively charged ertapenem (Singh et al. 2015).
NfpA/NfpB of Nocardia farcinica
NfpA (234aas) (Q5YZF6)
NfpB (229aas) (Q5YZF5)
MspA porin homologue (200aas; 1 N-terminal TMS)
MspA porin of Nocardia brasiliensis (H5RPX4)
MspA family member (263aas; 1 N-terminal TMS)
MspA porin of Segniliparus rotundus (D6Z9R0)
MspA porin homologue (212 aas; 1 N-terminal TMS)
MspA porin of Mycobacterium abscessus
Porin of Rhodococcus erythropolis
Putative porin of 222 aas.
MspA homologue of Gordonia soli
Putative porin, MspA of 221 aas.
MspA of Gordonia bronchialis