This family is likely to be an S-adenosyl-L-methionine (SAM)-dependent RNA methyltransferase [1]. It is responsible for N1-methylation of pseudouridine 54 in archaeal tRNAs [2].

1: Crystal structure of Mj1640/DUF358 protein reveals a putative SPOUT-class RNA methyltransferase. Chen HY, Yuan YA; J Mol Cell Biol. 2010;2:366-374. PMID:21098051

2: Identification of the enzyme responsible for N1-methylation of pseudouridine 54 in archaeal tRNAs. Wurm JP, Griese M, Bahr U, Held M, Heckel A, Karas M, Soppa J, Wohnert J; RNA. 2012;18:412-420. PMID:22274954