Comparative genomics and functional analysis of th

Authors: Linda Jeanguenin Aurora LaraNúñez Dmitry A Rodionov Andrei L Osterman Nataliya Y Komarova Doris Rentsch Jesse F Gregory Andrew D Hanson

Publish Date: 2011/09/28

Volume: 12, Issue: 1, Pages: 25-34

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Abstract

The transporters that mediate uptake of nicotinate and its Nmethyl derivative trigonelline are not known in plants and certain mammalian nicotinate transporters also remain unidentified Potential candidates for these missing transporters include proteins from the ubiquitous NiaP family In bacteria niaP genes often belong to NADrelated regulons and genetic evidence supports a role for Bacillus subtilis and Acinetobacter baumannii NiaP proteins in uptake of nicotinate or nicotinamide Other bacterial niaP genes are however not in NADrelated regulons but cluster on the chromosome with cholinerelated eg Ralstonia solanacearum and Burkholderia xenovorans or thiaminrelated eg Thermus thermophilus genes implying that they might encode transporters for these compounds Radiometric uptake assays using Lactococcus lactis cells expressing NiaP proteins showed that B subtilis R solanacearum and B xenovorans NiaP transport nicotinate via an energydependent mechanism Likewise NiaP proteins from maize GRMZM2G381453 GRMZM2G066801 and GRMZM2G081774 Arabidopsis At3g13050 and mouse SVOP transported nicotinate the Arabidopsis protein also transported trigonelline In contrast T thermophilus NiaP transported only thiamin None of the proteins tested transported choline or the thiazole and pyrimidine products of thiamin breakdown The maize and Arabidopsis NiaP proteins are the first nicotinate transporters reported in plants the Arabidopsis protein is the first trigonelline transporter and mouse SVOP appears to represent a novel type of mammalian nicotinate transporter More generally these results indicate that specificity for nicotinate is conserved widely but not absolutely among pro and eukaryotic NiaP family proteinsThis work was supported in part by US National Science Foundation award IOS1025398 to ADH by Swiss National Science Foundation grant 31003A 127340 to DR and by an endowment from the C V Griffin Sr Foundation The work of DAR and ALO was supported by the US Department of Energy DOE Office of Biological and Environmental Research BER as part of BER’s Genomic Science Program GSP originating Foundational Scientific Focus Area FSA at the Pacific Northwest National Laboratory PNNL The work of DAR was also supported by award R01GM077402 from the National Institute of General Medical Sciences We thank Dr Edmund Kunji for his generous advice and encouragement and M Ziemak for technical support

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