Conserved residues Arg188 and Asp302 are critical for active site organization and catalysis in human ABO(H) blood group A and B glycosyltransferases

Distributions and prognostic effects of ABO/Rh blood groups in patients with HER2/neu positive gastric and gastroesophageal junction cancer

BACKGROUND

The aim of study was to look at ABO/Rh blood types frequency and prognostic significance in patients with HER2/neu positive gastric cancer.

METHODS

The study was designed retrospectively. Clinicopathological characteristics, treatment approaches, and the ABO/Rh blood groups features were noted. The ABO/Rh blood types for patients and healthy donors were compared by the Chi-square method.

RESULTS

The average age was 61 years. The average survival time was 17.9 months (13.2-22.5). ABO blood types frequencies were not similar between patients (25.9% O, 6.3% AB, 57.1% A, and 10.7% B) and control group (34.9% O, 7.9% AB, 41.9% A, and 15.3% B) (P = 0.01). Patients and controls had the same Rh factor distribution (P = 0.07).

CONCLUSIONS

We showed that A blood group frequency was increased in patients with HER2/neu receptor-positive gastric cancer than in a healthy population. Also, we detected that the frequency of O blood type was decreased. ABO/Rh blood types were not linked with prognosis for overall survival.

The wclY gene of Escherichia coli serotype O117 encodes an α1,4-glucosyltransferase with strict acceptor specificity but broad donor specificity

The O antigen of enterotoxigenic Escherichia coli serotype O117 consists of repeating units with the structure [-D-GalNAcβ1-3-L-Rhaα1-4-D-Glcα1-4-D-Galβ1-3-D-GalNAcα1-4]n. A related structure is found in E. coli O107 where Glc is replaced by a GlcNAc residue. The O117 and O107 antigen biosynthesis gene clusters are homologous and reveal the presence of four putative glycosyltransferase (GT) genes, wclW, wclX, wclY and wclZ, but the enzymes have not yet been biochemically characterized. We show here that the His6-tagged WclY protein expressed in E. coli Lemo21(DE3) cells is an α1,4-Glc-transferase that transfers Glc to the Gal moiety of Galβ1-3GalNAcα-OPO3-PO3-phenoxyundecyl as a specific acceptor and that the diphosphate moiety of this acceptor is required. WclY utilized UDP-Glc, TDP-Glc, ADP-Glc, as well as UDP-GlcNAc, UDP-Gal or UDP-GalNAc as donor substrates, suggesting an unusual broad donor specificity. Activity using GDP-Man suggested the presence of a novel Man-transferase in Lemo21(DE3) cells. Mutations of WclY revealed that both Glu residues of the Ex7E motif within the predicted GT domain are essential for activity. High GlcNAc-transferase (GlcNAc-T) activities of WclY were created by mutating Arg194 to Cys. A triple mutant identical to WclY in E. coli O107 was identified as an α1,4 GlcNAc-T. The characterization of WclY opens the door for the development of antibacterial approaches.

Comparative analysis of intact glycopeptides from mannose receptor among different breast cancer subtypes using mass spectrometry

Breast cancer is a highly heterogeneous disease, encompassing a number of biologically distinct entities with specific pathologic features and biological behaviors. In the preliminary experiments, we identified several glycosylation sites of mannose receptors in different breast cancer subtypes and showed that the mannose receptors could be a potential marker for breast cancer. However, the glycan composition on each site is still unknown because the glycan was removed by PNGase F in previous work. Analysis of intact glycopeptides can provide the information of both the glycan composition and the glycosylation site, which can further help to reveal the difference of glycosylation in the four subtypes of breast cancer. In this work, we analyzed the intact glycopeptides of the mannose receptors in serum from breast cancer patients using isobaric tags for relative and absolute quantitation (iTRAQ) and LC-MS/MS. In total, 7 glycosylation sites and 12 glycan types corresponding to 26 intact glycopeptides were characterized from the four subtypes of breast cancer. Among them, 11 glycopeptides can be used to differentiate the subtypes of breast cancer, which further supported the previous conclusion that mannose receptor can be used as a potential marker for the identification of breast cancer subtypes.

Two novel mutations p. L319V and p. L91P in ABO glycosyltransferases lead to Ael and Bel phenotypes

BACKGROUND

Mutations of the ABO gene may cause the dysfunction of ABO glycosyltransferase (GT) that can result in weak ABO phenotypes. Here, we identified two novel weak ABO subgroup alleles and explored their mechanisms that caused A_el and B_el phenotypes.

MATERIALS AND METHODS

The ABO phenotyping and genotyping were performed by serological studies and direct DNA sequencing of the ABO gene. The role of the novel mutations were evaluated by a three-dimensional model, predicting protein structure changes, and in vitro expression assay. The total glycosyltransferase transfer capacity in supernatant of transfected cells was examined.

RESULTS

We identified a mutation c. 955C>G (p. L319V) of A allele in an A_el subject and a mutation c. 272T>C (p. L91P) of B allele in a B_el subject. In silico analysis showed that the mutation p. L319V of the A allele and p. L91P of the B allele may change the local conformation of GT and impair the catalysis of H to A or B antigen conversion. In vitro expression study showed that mutation p. L319V impaired H to A antigen conversion, although it did not affect the expression of glycosyltransferase A.

CONCLUSIONS

Two novel "el"-type ABO subgroup alleles were identified. Both of the two novel mutations can change the local conformation of GTs and reduce protein stability. GTA mutation p. L319V can impair the conversion from H to A antigen and causes the A_el phenotype.

Deep evolutionary analysis reveals the design principles of fold A glycosyltransferases

Glycosyltransferases (GTs) are prevalent across the tree of life and regulate nearly all aspects of cellular functions. The evolutionary basis for their complex and diverse modes of catalytic functions remain enigmatic. Here, based on deep mining of over half million GT-A fold sequences, we define a minimal core component shared among functionally diverse enzymes. We find that variations in the common core and emergence of hypervariable loops extending from the core contributed to GT-A diversity. We provide a phylogenetic framework relating diverse GT-A fold families for the first time and show that inverting and retaining mechanisms emerged multiple times independently during evolution. Using evolutionary information encoded in primary sequences, we trained a machine learning classifier to predict donor specificity with nearly 90% accuracy and deployed it for the annotation of understudied GTs. Our studies provide an evolutionary framework for investigating complex relationships connecting GT-A fold sequence, structure, function and regulation.

Carbohydrates are one of the major groups of large biological molecules that regulate nearly all aspects of life. Yet, unlike DNA or proteins, carbohydrates are made without a template to follow. Instead, these molecules are built from a set of sugar-based building blocks by the intricate activities of a large and diverse family of enzymes known as glycosyltransferases.

An incomplete understanding of how glycosyltransferases recognize and build diverse carbohydrates presents a major bottleneck in developing therapeutic strategies for diseases associated with abnormalities in these enzymes. It also limits efforts to engineer these enzymes for biotechnology applications and biofuel production.

Taujale et al. have now used evolutionary approaches to map the evolution of a major subset of glycosyltransferases from species across the tree of life to understand how these enzymes evolved such precise mechanisms to build diverse carbohydrates. First, a minimal structural unit was defined based on being shared among a group of over half a million unique glycosyltransferase enzymes with different activities. Further analysis then showed that the diverse activities of these enzymes evolved through the accumulation of mutations within this structural unit, as well as in much more variable regions in the enzyme that extend from the minimal unit.

Taujale et al. then built an extended family tree for this collection of glycosyltransferases and details of the evolutionary relationships between the enzymes helped them to create a machine learning framework that could predict which sugar-containing molecules were the raw materials for a given glycosyltransferase. This framework could make predictions with nearly 90% accuracy based only on information that can be deciphered from the gene for that enzyme.

These findings will provide scientists with new hypotheses for investigating the complex relationships connecting the genetic information about glycosyltransferases with their structures and activities. Further refinement of the machine learning framework may eventually enable the design of enzymes with properties that are desirable for applications in biotechnology.

Molecular determinants for ligand binding at Nav1.4 and Nav1.7 channels: Experimental affinity results analyzed by molecular modeling

Here, we focused on exploring the selectivity mechanism against Nav1.7 over Nav1.4 due to different binding modes of two selected inhibitors. By the superposition of Nav1.7 and Nav1.4 proteins, we selected the most homologous chain of Nav1.7 with Nav1.4, defining the active site of Nav1.4-VSD4 based on the aryl sulfonamide binding site of Nav1.7-VSD4. Comparison of the conformations exhibited by Tyr1386 (Nav1.4) and Tyr1537 (Nav1.7) suggested that the steric hindrance caused by Tyr1386 owned primary influence on inhibition selectivity, which was further verified through molecular docking and MD simulation of two representative inhibitors. Our finding would be helpful for discovery of selective Nav1.7 inhibitors over Nav1.4.

Quick-soaking of crystals reveals unprecedented insights into the catalytic mechanism of glycosyltransferases

Glycosyltransferases (GTs) catalyze the transfer of a sugar moiety from nucleotide-sugar or lipid-phospho-sugar donors to a wide range of acceptor substrates, generating a remarkable amount of structural diversity in biological systems. Glycosyl transfer reactions can proceed with either inversion or retention of the anomeric configuration with respect to the sugar donor substrate. In this chapter, we discuss the application of a quick soaking method of substrates and products into protein crystals to visualize native ternary complexes of retaining glycosyltransferases. The crystal structures provide different snapshots of the catalytic cycle, including the Michaelis complex. During this sequence of events, we visualize how the enzyme guides the substrates into the reaction center where the glycosyl transfer reaction takes place, and unveil the mechanism of product release, involving multiple conformational changes not only in the substrates and products but also in the enzyme. The methodology described here provides unprecedented insights into the catalytic mechanism of glycosyltransferases at the molecular level, and can be applied to the study a myriad of enzymatic mediated reactions.