Abstract
The Rhodococcus erythropolis gene DYC18_RS18060 (1437 bp) putatively codes for a secondary transporter of the Nucleobase Cation Symporter-1 (NCS-1) protein family (478 amino acids). The DYC18_RS18060 gene was successfully cloned from R. erythropolis genomic DNA with addition of EcoRI and PstI restriction sites at the 5′ and 3′ ends, respectively, using PCR technology. The amplified gene was introduced into IPTG-inducible plasmid pTTQ18 immediately upstream of the sequence coding for a His6-tag. The construct was transformed into Escherichia coli BL21(DE3), then amplified expression of the DYC18_RS18060-His6 protein was achieved with detection by SDS-PAGE and western blotting. Computational methods predicted that DYC18_RS18060 has a molecular weight of 51.1 kDa and isoelectric point of 6.58. The protein was predicted to be hydrophobic in nature (aliphatic index 113.24, grand average of hydropathicity 0.728) and to form twelve transmembrane spanning α-helices with both N- and C-terminal ends at the cytoplasmic side of the membrane. Whilst database sequence similarity searches and phylogenetic analysis suggested that the substrate of DYC18_RS18060 could be cytosine, this was not certain based on comparisons of residues involved in substrate binding in experimentally characterised NCS-1 proteins. This study has laid foundations for further structural and functional studies of DYC18_RS18060 and other NCS-1 proteins.
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Highlights
The Nucleobase Cation Symporter-1 (NCS-1) family of secondary active transport proteins is widespread in bacteria, archaea, fungi and plants [1,2,3,4,5,6,7,8,9]
There is a glaring lack of information available about NCS-1 proteins determined by experimental studies, so we have undertaken study of further bacterial NCS-1 proteins
The PCR primers designed for cloning and amplifying the DYC18_RS18060 gene from R. erythropolis with a His6-tag were predicted to be free of dimers or other secondary structures
Summary
The Nucleobase Cation Symporter-1 (NCS-1) family of secondary active transport proteins is widespread in bacteria, archaea, fungi and plants [1,2,3,4,5,6,7,8,9]. The principal function of NCS-1 proteins appears to be in salvage pathways where their role is uptake of nucleobases, nucleosides, hydantoins and other similar compounds from the environment. This employs a symport mechanism driven by a gradient of protons or sodium ions [6]. Whilst Mhp is the only NCS-1 protein with high-resolution structures determined, 27 other NCS-1 proteins (5 bacterial, 16 fungal, 6 plant) have been characterised experimentally [6, 9, 23,24,25,26,27]. There is a glaring lack of information available about NCS-1 proteins determined by experimental studies, so we have undertaken study of further bacterial NCS-1 proteins
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