The Histidine Triad (HIT) motif, His-x-His-x-His-x-x (x, ahydrophobic amino acid) was identified as being highly conserved in a variety of organisms [, ]. On the basis of sequence, substrate specificity, structure, evolution and mechanism, HIT proteins are classified into three branches: the Hint branch, which consists of adenosine 5' -monophosphoramide hydrolases, the FHIT branch, that consists of diadenosine polyphosphate hydrolases, and the GalT branch consisting of specific nucloside monophosphate transferases [, ]. In budding yeast Hnt1 has been shown to have adenosine monophosphoramidase activity and function as positive regulators of Cdk7/Kin28 in vivo [, ]. FHIT plays a very important role in the development of tumours. In fact, FHIT deletions are among the earliest and most frequent genetic alterations in the development of tumours [, ]. The third branch of the HIT superfamily, which includes GalT homologues, contains a related His-X-His-X-Gln motif and transfers nucleoside monophosphate moieties to phosphorylated second substrates ratherthan hydrolysing them [].
Galactose-1-phosphate uridyl transferase catalyses the conversion of UDP-glucose and alpha-D-galactose 1-phosphate to alpha-D-glucose 1-phosphate and UDP-galactose during galactose metabolism. The enzyme is present in prokaryotes and eukaryotes. Defects in GalT in humans is the cause of galactosemia, an inherited disorder of galactose metabolism that leads to jaundice, cataracts and mental retardation.This domain describes the C-terminal of Galactose-1-phosphate uridyl transferase. SCOP reports fold duplication of the C-terminal with the N-terminal domain. Both are involved in Zn and Fe binding
Galactose-1-phosphate uridyl transferase catalyses the conversion of UDP-glucose and alpha-D-galactose 1-phosphate to alpha-D-glucose 1-phosphate and UDP-galactose during galactose metabolism. The enzyme is present in prokaryotes and eukaryotes. Defects in GalT in humans is the cause of galactosemia, an inherited disorder of galactose metabolism that leads to jaundice, cataracts and mental retardation.This domain describes the C-terminal of Galactose-1-phosphate uridyl transferase. SCOP reports fold duplication of the C-terminal with the N-terminal domain. Both are involved in Zn and Fe binding
This group is related to , galactose-1-phosphate uridylyltransferases (GalT; ). is a member of the HIT domain superfamily based on structural fold []and has a signature HXHXQ. Members of this group are shorter than members by ~100 residues, but have considerable sequence similarity, including the signature. Galactose-1-phosphate uridylyltransferase is involved in the metabolism of galactose via the Leloir pathway []. GalT catalyses the transfer of a uridine 5 -phosphoryl group from UDP-galactose 1-phosphate. It consists of two identical subunits; the active site is formed by amino acid residues from both subunits of the dimer [, ].
FHIT (fragile histidine) proteins are related to the HIT family members that carry a motif HxHxH/Qxx (x, is a hydrophobic amino acid) []. On the basis of sequence, substrate specificity, structure, evolution and mechanism, HIT proteins are classified into three branches: the Hint branch, which consists of adenosine 5' -monophosphoramide hydrolases, the FHIT branch, that consists of diadenosine polyphosphate hydrolases, and the GalT branch consisting of specific nucloside monophosphate transferases [, , ]. FHIT plays a very important role in the development of tumours. In fact, FHIT deletions are among the earliest and most frequent genetic alterations in the development of tumours [, ].
HIT (Histidine triad) proteins, named for a motif related to the sequence HxHxH/Qxx (x, a hydrophobic amino acid), are a superfamily of nucleotide hydrolases and transferases that act on the alpha-phosphate of ribonucleotides. On the basis of sequence, substrate specificity, structure, evolution and mechanism, HIT proteins are classified in the literature into three major branches: the Hint branch, which consists of adenosine 5' -monophosphoramide hydrolases, the Fhit branch, which consists of diadenosine polyphosphate hydrolases, and the GalT branch, consisting of specific nucleoside monophosphate transferases. Further sequence analysis reveals several new, closely related, yet uncharacterised subgroups. This group includes bacterial proteins which are members from the Hint branch of hydrolases. For additional information please see [, , , , , ].
HINT (histidine triad nucleotide-binding protein) are related to the HIT family members that carry a motif HxHxH/Qxx (x, is a hydrophobic amino acid) []. On the basis of sequence, substrate specificity, structure, evolution and mechanism, HIT proteins are classified into three branches: the Hint branch, which consists of adenosine 5' -monophosphoramide hydrolases, the FHIT branch, that consists of diadenosine polyphosphate hydrolases, and the GalT branch consisting of specific nucloside monophosphate transferases []. HINT family includes members from all three forms of cellular life. In budding yeast Hnt1 has been shown to have adenosine monophosphoramidase activity []. It is involved in secretion, peroxisome formation and gene expression [, ]. The bacterial and archaeal members of this family are mostly uncharacterised.
