9.A.23 The Niacin/Nicotinamide Transporter (NNT) Family

NiaY (BH3254) of Bacillus halodurans C-125 is a putative niacin (vitamin B3 or nicotinic acid)/nicotinamide transporter (Rodionov et al., 2009). The protein has eight predicted TMSs and is homologous to the PTS Enzyme IIC components of the glucose/fructose families (4e-7). In addition, similarity was observed for TMSs 1-6 with TMSs 7-12 of an MFS transporters (2.A.1.35.2; RosA; 6e-4). In spite of the sequence similarity with PTS permeases, this protein is placed in a new family (9.A.23) because of its dissimilar predicted function and PTS-independent mechanism of action.

The generalized reaction predicted for NiaY is:

niacin and/or nicotinamide (out) ⇌ niacin and/or nicotinamide (in)



Rodionov, D.A., P. Hebbeln, A. Eudes, J. ter Beek, I.A. Rodionova, G.B. Erkens, D.J. Slotboom, M.S. Gelfand, A.L. Osterman, A.D. Hanson, and T. Eitinger. (2009). A novel class of modular transporters for vitamins in prokaryotes. J. Bacteriol. 191: 42-51.

Rodionov, D.A., X. Li, I.A. Rodionova, C. Yang, L. Sorci, E. Dervyn, D. Martynowski, H. Zhang, M.S. Gelfand, and A.L. Osterman. (2008). Transcriptional regulation of NAD metabolism in bacteria: genomic reconstruction of NiaR (YrxA) regulon. Nucleic Acids Res 36: 2032-2046.


TC#NameOrganismal TypeExample

The putative niacin/nicotinamide transporter, NiaY (Rodionov et al. 2008)


NiaY of Bacillus halodurans (Q9K7V5)


Uncharacterized protein of 390 aas and 11 TMSs.  Its gene maps adjacent to and in the same operon with a nicotinate phosphoribosyl transferase gene and a MATE family (TC# 2.A.66) exporter gene.


UP of Acholeplasma laidlawii