This is a ferredoxin-like domain of NOL1/NOP2/Sun domain family member 5, found at the N-terminal of the methyltransferase domain [1,4]. NSUN5 is a SAM-dependent methyltransferase that specifically methylates the C(5) position of cytosine 3782 in 28S rRNA [2,3].

1: Crystal structure of human p120 homologue protein PH1374 from Pyrococcus horikoshii. Ishikawa I, Sakai N, Tamura T, Yao M, Watanabe N, Tanaka I; Proteins. 2004;54:814-816. PMID:14997580

2: Yeast Nop2 and Rcm1 methylate C2870 and C2278 of the 25S rRNA, respectively. Sharma S, Yang J, Watzinger P, Kotter P, Entian KD; Nucleic Acids Res. 2013;41:9062-9076. PMID:23913415

3: Loss of the ribosomal RNA methyltransferase NSUN5 impairs global protein synthesis and normal growth. Heissenberger C, Liendl L, Nagelreiter F, Gonskikh Y, Yang G, Stelzer EM, Krammer TL, Micutkova L, Vogt S, Kreil DP, Sekot G, Siena E, Poser I, Harreither E, Linder A, Ehret V, Helbich TH, Grillari-Voglauer R, Jansen-Durr P, Kos M, Polacek N, Grillari J, Schosserer M; Nucleic Acids Res. 2019;47:11807-11825. PMID:31722427