This family includes the queT gene encoding a hypothetical integral membrane protein with 5 predicted transmembrane regions. The queT genes in Firmicutes are often preceded by the PreQ1 (7-aminomethyl-7-deazaguanine) riboswitches of two distinct classes [1-2], suggesting involvement of the QueT transporters in uptake of a queuosine biosynthetic intermediate.

1: A riboswitch selective for the queuosine precursor preQ1 contains an unusually small aptamer domain. Roth A, Winkler WC, Regulski EE, Lee BW, Lim J, Jona I, Barrick JE, Ritwik A, Kim JN, Welz R, Iwata-Reuyl D, Breaker RR; Nat Struct Mol Biol. 2007;14:308-317. PMID:17384645

2: Confirmation of a second natural preQ1 aptamer class in Streptococcaceae bacteria. Meyer MM, Roth A, Chervin SM, Garcia GA, Breaker RR; RNA. 2008;14:685-695. PMID:18305186