<p> This subfamily contains the tRNA-i(6)A37 modification enzyme, MiaB (<db_xref db="TIGRFAMS" dbkey="TIGR01574"/>). The phylogenetic tree indicates 4 distinct clades, one of which corresponds to MiaB. The other three clades are modelled by hypothetical equivalogs (<db_xref db="TIGRFAMS" dbkey="TIGR01125"/>, <db_xref db="TIGRFAMS" dbkey="TIGR01579"/> and <db_xref db="TIGRFAMS" dbkey="TIGR01578"/>). Together, the four models hit every sequence hit by the subfamily model without any overlap between them. This subfamily is apparently a part of a larger superfamily of enzymes utilizing both a 4Fe4S cluster and S-adenosyl methionine (SAM) to initiate radical reactions. MiaB acts on a particular isoprenylated Adenine base of certain tRNAs causing thiolation at an aromatic carbon, and probably also transferring a methyl group from SAM to the thiol. The particular substrate of the three other clades is unknown but may be very closely related. </p>