AC   MF_00168;
DC   Protein; auto
c?   <OC:Bacteria>
TR   HAMAP; MF_00168; -; 1; level=0
XX
Names: Q_tRNA_Tgt
XX
ID   TGT
case <OC:Bacteria>
DE   RecName: Full=Queuine tRNA-ribosyltransferase;
DE            EC=2.4.2.29;
DE   AltName: Full=Guanine insertion enzyme;
DE   AltName: Full=tRNA-guanine transglycosylase;
else case <OC:Archaea>
DE   RecName: Full=Putative queuine tRNA-ribosyltransferase;
DE            EC=2.4.2.29;
DE   AltName: Full=Guanine insertion enzyme;
DE   AltName: Full=tRNA-guanine transglycosylase;
end case
GN   Name=tgt;
XX
CC   -!- FUNCTION: Catalyzes the base-exchange of a guanine (G) residue with the
CC       queuine precursor 7-aminomethyl-7-deazaguanine (PreQ1) at position 34
CC       (anticodon wobble position) in tRNAs with GU(N) anticodons (tRNA-Asp,
CC       -Asn, -His and -Tyr). Catalysis occurs through a double-displacement
CC       mechanism. The nucleophile active site attacks the C1' of nucleotide 34
CC       to detach the guanine base from the RNA, forming a covalent enzyme-RNA
CC       intermediate. The proton acceptor active site deprotonates the incoming
CC       PreQ1, allowing a nucleophilic attack on the C1' of the ribose to form
CC       the product. After dissociation, two additional enzymatic reactions on
CC       the tRNA convert PreQ1 to queuine (Q), resulting in the hypermodified
CC       nucleoside queuosine (7-(((4,5-cis-dihydroxy-2-cyclopenten-1-
CC       yl)amino)methyl)-7-deazaguanosine).
CC   -!- CATALYTIC ACTIVITY:
CC       Reaction=7-aminomethyl-7-carbaguanine + guanosine(34) in tRNA = 7-
CC         aminomethyl-7-carbaguanosine(34) in tRNA + guanine;
CC         Xref=Rhea:RHEA:24104, Rhea:RHEA-COMP:10341, Rhea:RHEA-COMP:10342,
CC         ChEBI:CHEBI:16235, ChEBI:CHEBI:58703, ChEBI:CHEBI:74269,
CC         ChEBI:CHEBI:82833; EC=2.4.2.29;
case <FTGroup:1>
CC   -!- COFACTOR:
CC       Name=Zn(2+); Xref=ChEBI:CHEBI:29105;
CC       Note=Binds 1 zinc ion per subunit.;
end case
case <OC:Bacteria>
CC   -!- PATHWAY: tRNA modification; tRNA-queuosine biosynthesis.
end case
CC   -!- SUBUNIT: Homodimer. Within each dimer, one monomer is responsible for
CC       RNA recognition and catalysis, while the other monomer binds to the
CC       replacement base PreQ1.
CC   -!- SIMILARITY: Belongs to the queuine tRNA-ribosyltransferase family.
XX
DR   Pfam; PF01702; TGT; 1; trigger=no
DR   NCBIfam; TIGR00430; Q_tRNA_tgt; 1; trigger=no
DR   NCBIfam; TIGR00449; Tgt_general; 1; trigger=no
XX
case <OC:Bacteria>
KW   Queuosine biosynthesis
end case
KW   Glycosyltransferase
KW   Transferase
KW   tRNA processing
case <FTGroup:1>
KW   Metal-binding
KW   Zinc
end case
XX
GO   GO:0008479; F:tRNA-guanosine(34) queuine transglycosylase activity
case <OC:Bacteria>
GO   GO:0008616; P:queuosine biosynthetic process
end case
GO   GO:0006400; P:tRNA modification
XX
FT   From: TGT_ZYMMO (P28720)
FT   BINDING         102..106
FT                   /ligand="substrate"
FT   Condition: D-S-G-G-[FY]
FT   REGION          261..267
FT                   /note="RNA binding"
FT   Condition: G-[VIG]-G-x(4)
FT   REGION          285..289
FT                   /note="RNA binding; important for wobble base 34
FT                   recognition"
FT   Condition: [TA]-[RK]-x(2)-R
FT   ACT_SITE        102
FT                   /note="Proton acceptor"
FT   Condition: D
FT   ACT_SITE        280
FT                   /note="Nucleophile"
FT   Condition: D
FT   BINDING         318
FT                   /ligand="Zn(2+)"
FT                   /ligand_id="ChEBI:CHEBI:29105"
FT   Group: 1; Condition: C
FT   BINDING         320
FT                   /ligand="Zn(2+)"
FT                   /ligand_id="ChEBI:CHEBI:29105"
FT   Group: 1; Condition: C
FT   BINDING         323
FT                   /ligand="Zn(2+)"
FT                   /ligand_id="ChEBI:CHEBI:29105"
FT   Group: 1; Condition: C
FT   BINDING         349
FT                   /ligand="Zn(2+)"
FT                   /ligand_id="ChEBI:CHEBI:29105"
FT   Group: 1; Condition: H
FT   BINDING         156
FT                   /ligand="substrate"
FT   Condition: D
FT   BINDING         203
FT                   /ligand="substrate"
FT   Condition: Q
FT   BINDING         230
FT                   /ligand="substrate"
FT   Condition: G
XX
Size: 361-403;
Related: None;
Template: P28720; P0A847;
Scope:
 Bacteria
 Archaea
Fusion:
 Nter: None
 Cter: None
Duplicate: None
Plasmid: None
Comments: None
XX
# Revision 1.42 2024/01/31
//