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)