Gene Ontology annotation through association of InterPro records with GO terms
Manual transfer of experimentally-verified manual GO annotation data to orthologs by curator judgment of sequence similarity
Annotation inferences using phylogenetic trees
Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location vocabulary mapping, accompanied by conservative changes to GO terms applied by UniProt
Combined Automated Annotation using Multiple IEA Methods
UniProtKB entry U3KPV4 (A3LT2_HUMAN), Alpha-1,3-galactosyltransferase 2
-
UniProt predicts an N-terminal transmembrane signal anchor consistent with a single-pass type-II membrane protein.
"FT TRANSMEM 13..32"
-
The UniProt entry remains at transcript-level protein evidence.
"PE 2: Evidence at transcript level;"
PANTHER PTHR10462 glycosyltransferase-related family entries
PANTHER PTHR10462 glycosyltransferase-related family metadata
Humans lack iGb3 due to the absence of functional iGb3-synthase: implications for NKT cell development and transplantation.
-
Extensive cross-exon RT-PCR failed to detect correctly spliced A3GALT2/iGb3S mRNA in the tested adult tissues and dendritic cells.
"Despite using numerous primer combinations, including forward primers from exons 2, 3, or 4 with a reverse primer from exon 5 (Figure 2C), we were unable to detect any products of the correct size to suggest spliced iGb3S mRNA in any human tissue examined (Figure 2D), even when a high cycle number (up to 40) was used (unpublished data)."
-
Rat/human chimeras carrying most or all of the human catalytic domain did not synthesize the Gal-alpha(1,3)-Gal epitope.
"The chimeric molecule containing the majority of the catalytic domain of human iGb3S (rat/human(exon5)-iGb3S) was unable to synthesise the Galα(1,3)Gal epitope as staining was not observed with 15.101 or human anti-Gal Ig (Figure 3B). A second chimeric molecule comprising the entire human catalytic domain, exon 4 together with exon 5 (rat/human(exon4,5)-iGb3S), was also unable to synthesize Galα(1,3)Gal (Figure 3B)."
-
The inactive chimeras were translated and showed Golgi-like trafficking, arguing against failed expression or gross mistargeting in that assay.
"Detection of the FLAG epitope in both chimeric enzymes confirmed that the absence of Galα(1,3)Gal synthesis was not due to impaired translation or expression (Figure S2A). As glycosyltransferases are integral membrane proteins of the Golgi complex where oligosaccharides are synthesized, perinuclear staining (Golgi-like) confirmed correct trafficking of the chimeric enzymes (Figure S2B)."
Lack of iGb3 and Isoglobo-Series Glycosphingolipids in Pig Organs Used for Xenotransplantation: Implications for Natural Killer T-Cell Biology.
-
The assembled human iGb3S construct produced MS-detectable iGb3 and iGb4 after CHO-cell overexpression, but activity was very weak and no B4/B5/B6 elongation was detected.
"Our results showed that human iGb3 synthase initiated the synthesis of both iGb3 (Fig. 6A) and iGb4 (Fig. 6B), as measured by LIT-MSn technology. However, the human iGb3 synthase showed very weak activity even in the CHO cell transfection experiment and could not further elongate iGb3 to B4, B5, and B6 GSLs (Table 1)."
-
Exon 1 and the start of exon 2 were introduced by an amplification primer rather than recovered as an intact endogenous full-length transcript.
"The exon 1 and the beginning of exon 2 were directly added by PCR reaction using a long primer F1"
-
iGb3 signature ions were found in monocyte-derived dendritic-cell preparations from five donors, but product detection does not causally identify A3GALT2 as the source.
"iGb3 signature ions were present in all of the five human dendritic cell samples generated from monocytes obtained from five different healthy donors (Fig. 1A), representing 1.2% to 10.8% of the iGb3/Gb3 isomer mixtures in some iGb3-containing MS1 trihexosylceramide ions."
Sensitive detection of isoglobo and globo series tetraglycosylceramides in human thymus by ion trap mass spectrometry.
-
Ion-trap mass spectrometry identified iGb4 in human thymus, an indirect observation compatible with isoglobo-series synthesis but not attributable to A3GALT2 by this experiment.
"report the identification of isoglobotetraglycosylceramide in a CHO cell line transfected by iGb3 synthase, as well as in human thymus."
Human knockouts and phenotypic analysis in a cohort with a high rate of consanguinity.
-
Two predicted p.Thr106SerfsTer4 homozygotes had markedly reduced fasting C-peptide and insulin; the authors explicitly considered human A3GALT2 biology uncertain.
"Alpha-1,3-galactosyltransferase 2 (encoded by A3GALT2) catalyzes the formation of the Gal-α1-3Galβ1-4GlcNAc-R (α-gal) epitope; the biological role of this enzyme in humans is uncertain.17 At A3GALT2, we identified two participants homozygous for a frameshift mutation, p.Thr106SerfsTer4. Compared with non-carriers, p.Thr106SerfsTer4 homozygotes both had dramatically reduced concentrations of fasting C-peptide (−97.4%; P = 6 × 10−12) and insulin (−92.3%; P = 1 × 10−4)."
-
The study cautions that predicted loss-of-function calls require experimental confirmation of transcript or protein loss.
"However, for any given pLoF, experimental validation will be required to prove loss of gene function (e.g., targeted assays such as RT-PCR of transcript and/or Western blot of protein to confirm its absence in the relevant tissue)."
Amino acid substitutions at sugar-recognizing codons confer ABO blood group system-related α1,3 Gal(NAc) transferases with differential enzymatic activity.
-
The paper summarizes prior evidence as indicating that humans lack functional A3GALT2/iGb3S activity.
"For instance, humans may have functional AT and/or BT, depending on the polymorphic status at the ABO genetic locus, but they carry none of the functional GBGT1, A3GALT2, or GGTA1 genes nor exhibit any of FS, iGb3S, or GT activities26–29."
-
The iGb3S construct experimentally tested in this work was rat, not human.
"Firstly, we performed polymerase chain reaction (PCR) using appropriate primers and rat A3galt2-201 cDNA cloned in pCMV SPORT6 vector (OriGene) as template, subcloned the amplified DNA fragment into pSG5 vector (Stratagene), obtaining the rat iGb3S construct: R_A3GALT2."
APOL1 polymorphism modulates sphingolipid profile of human podocytes.
-
A3GALT2 RNA was undetectable in the authors' whole-transcriptome analysis of immortalized human podocytes; the underlying result was not shown.
"gene expression level of A3GALT2 was undetectable in whole-transcriptome analysis generated in human immortalized podocytes (HPs) and downloaded from the NCBI SRA database (accession number: SUB7456861; data not shown)."
Expression cloning of a new member of the ABO blood group glycosyltransferases, iGb3 synthase, that directs the synthesis of isoglobo-glycosphingolipids.
Long-term evolution of the CAZY glycosyltransferase 6 (ABO) gene family from fishes to mammals--a birth-and-death evolution model.
Human A3GALT2 enzyme constructs and glycan substrate specificity: focused OpenScientist report