Cloning and homology modeling of a potassium channel gene NKC1 from Nicotiana rustica

A novel potassium channel NKC1 was cloned through RT-PCR,degenerate primers PCR,and RACE protocol from potassium starvation Nicotiana rustica roots.The cDNA of NKC1 contained 2481 nucleotides and an ORF of 2481 nucleotides that encoded a protein of 826 amino acids(Mr 94.6KD kDaltons) with 6 predicted transmembrane domains.The amino acid sequence encoded by NKC1 cDNA showed high homology to that of potassium channels found in Solanum tuberosum(79%).Based on the primary and secondary structure analysis of NKC1,three-dimensional structure of active region of NKC1 was developed by homology modeling methods.The transcription level of NKC1 was more abundant in root tips than in other plant tissues and was up-regulated when exposed to potassium starvation.Transcription was significantly reduced by the addition of 5 mM NH+4 in the solution.These results suggested that NKC1 played an important role in potassium transportation in N.rustica.