This family has a TIM barrel-like fold with a deep C-terminal trefoil knot. The arrangement of its hydrophilic and hydrophobic surfaces are opposite to that of the classic TIM barrel proteins. It is likely to bind RNA [1], and may function as a methyltransferase [2,3].

1: Deep trefoil knot implicated in RNA binding found in an archaebacterial protein. Zarembinski TI, Kim Y, Peterson K, Christendat D, Dharamsi A, Arrowsmith CH, Edwards AM, Joachimiak A; Proteins. 2003;50:177-183. PMID:12486711

2: Structural and evolutionary bioinformatics of the SPOUT superfamily of methyltransferases. Tkaczuk KL, Dunin-Horkawicz S, Purta E, Bujnicki JM; BMC Bioinformatics. 2007;8:73. PMID:17338813

3: RNomics and Modomics in the halophilic archaea Haloferax volcanii: identification of RNA modification genes. Grosjean H, Gaspin C, Marck C, Decatur WA, de Crecy-Lagard V; BMC Genomics. 2008;9:470. PMID:18844986