The nucleobase cation symporter 1 of Chlamydomonas reinhardtii and that of the evolutionarily distant Arabidopsis thaliana display parallel function and establish a plant-specific solute transport profile.

摘要

Nucleobase biochemistry is essential during a plant’s life cycle. Purines and pyrimidines are central to nucleic acid biochemistry, ATP synthesis, carbohydrate, glycoprotein and phospholipid metabolism, as well as the biosynthesis of many secondary metabolites. Previous studies show the single cell alga Chlamydomonas reinhardtii is capable of importing purines as nitrogen sources. An analysis of the C. reinhardtii genome indicates the presence of at least three distinct gene families encoding for known nucleobase transporters. The nucleobase cation symporter 1 (NCS1) family of transport proteins has been shown to transport purine and pyrimidine nucleobases. In this study, the solute transport and binding properties for the sole C. reinhardtii NCS1 (CrNCS1) are determined using heterologous complementation in Saccharomyces cerevisiae. CrNCS1 is shown to act as a transporter of adenine, guanine, uracil, and allantoin. This substrate profile is parallel to that of the previously characterized Arabidopsis thaliana NCS1 suggesting that the solute specificity for plant NCS1 developed early in plant evolution. Also, the solute transport specificity seen in CrNCS1 and AtNCS1 shows a stark difference when compared to specificities of single cell fungal NCS1 proteins.