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Nuclear pore complex subunit Nro1 In fission yeast, this protein is a positive regulator of the stability of Sre1N, the sterol regulatory element-binding protein which is an ER membrane-bound transcription factor that controls adaptation to low oxygen-growth. In addition, the fission yeast Nro1 is a direct inhibitor of a protein that inhibits SreN1 degradation, Ofd1 (an oxoglutamate deoxygenase). The outcome of this reactivity is that Ofd1 acts as an oxygen sensor that regulates the binding of Nro1 to Ofd1 to control the stability of Sre1N. Solution of the structure of Nro1 reveals it to be made up of a number of TPR coils. TPR proteins are composed of three to 16 tandem peptide repeat motifs of 34 amino acids with degenerate sequence. The helical pairs adopt a helix-turn-helix anti-parallel arrangement with interacting helices. In general, TPR motifs are stacked together so that helix A from TPRn is packed between helix B from TPRn and helix A from TPRn+1. In Nro1, the 12 alpha helices forming the six TPR motifs are organized as follows from N terminus to C terminus - TPR1A, TPR1B, TPR2A, TPR2B, TPR3A, TPR3B, TPR4A, TPR4B, TPR5A, TPR5B, TPR6A, and TPR6B with the C-terminal helix (hC) running above the sixth TPR motif with an angle of approx 45 degrees with TPR6A and TPR6B. The corresponding TPRs structural motifs are longer (50 residues) than are canonical ones (34 amino acids) and are organized into two subdomains - Nro1-N (residues 55-225) and Nro1-C (residues 226-393). The Nro1/Etti protein plays a role in nuclear import suggesting that it is residues 4-19 that are interacting with Ofd1. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",