Abstract
N-acetylglutamate kinase (NAGK) is an enzyme of the arginine biosynthesis pathway. It is activated by the PII protein in cyanobacteria and shown to interact with PII in arabidopsis and rice. We identified the NAGK gene of Physcomitrella patens, PpNAGK1, in the genome sequence database. The predicted protein is 55% identical (90% similarity) with A. thliana NAGK. Similar to NAGK of other plants, PpNAGK1 was shown to be located in chloroplasts. The PpNAGK1 mRNA level was not affected by the cellular nitrogen status but was high in the light and low in the dark. These results suggested that the NAGK activity is regulated by light and/or photosynthetic products. Since the highly conserved Ser residue in the T-loop of PII, which is essential for interaction with NAGK in cyanobacteria, is replaced with Thr in the moss PII protein, we are examining whether PII interacts with NAGK in the moss.
