Crystallization and preliminary crystallographic analysis of GanB, a GH42 intracellular β-galactosidase from Geobacillus stearothermophilus

β-Galactosidase: a traditional enzyme given multiple roles through protein engineering

β-Galactosidases are crucial carbohydrate-active enzymes that naturally catalyze the hydrolysis of galactoside bonds in oligo- and disaccharides. These enzymes are commonly used to degrade lactose and produce low-lactose and lactose-free dairy products that are beneficial for lactose-intolerant people. β-galactosidases exhibit transgalactosylation activity, and they have been employed in the synthesis of galactose-containing compounds such as galactooligosaccharides. However, most β-galactosidases have intrinsic limitations, such as low transglycosylation efficiency, significant product inhibition effects, weak thermal stability, and a narrow substrate spectrum, which greatly hinder their applications. Enzyme engineering offers a solution for optimizing their catalytic performance. The study of the enzyme's structure paves the way toward explaining catalytic mechanisms and increasing the efficiency of enzyme engineering. In this review, the structure features of β-galactosidases from different glycosyl hydrolase families and the catalytic mechanisms are summarized in detail to offer guidance for protein engineering. The properties and applications of β-galactosidases are discussed. Additionally, the latest progress in β-galactosidase engineering and the strategies employed are highlighted. Based on the combined analysis of structure information and catalytic mechanisms, the ultimate goal of this review is to furnish a thorough direction for β-galactosidases engineering and promote their application in the food and dairy industries.

Cloning, Expression, Purification, and Characterization of a Novel β-Galactosidase/α-L-Arabinopyranosidase from Paenibacillus polymyxa KF-1

Glycosidases are essential for the industrial production of functional oligosaccharides and many biotech applications. A novel β-galactosidase/α-L-arabinopyranosidase (PpBGal42A) of the glycoside hydrolase family 42 (GH42) from Paenibacillus polymyxa KF-1 was identified and functionally characterized. Using pNPG as a substrate, the recombinant PpBGal42A (77.16 kD) was shown to have an optimal temperature and pH of 30 °C and 6.0. Using pNPαArap as a substrate, the optimal temperature and pH were 40 °C and 7.0. PpBGal42A has good temperature and pH stability. Furthermore, Na+, K+, Li+, and Ca2+ (5 mmol/L) enhanced the enzymatic activity, whereas Mn2+, Cu2+, Zn2+, and Hg2+ significantly reduced the enzymatic activity. PpBGal42A hydrolyzed pNP-β-D-galactoside and pNP-α-L-arabinopyranoside. PpBGal42A liberated galactose from β-1,3/4/6-galactobiose and galactan. PpBGal42A hydrolyzed arabinopyranose at C20 of ginsenoside Rb2, but could not cleave arabinofuranose at C20 of ginsenoside Rc. Meanwhile, the molecular docking results revealed that PpBGal42A efficiently recognized and catalyzed lactose. PpBGal42A hydrolyzes lactose to galactose and glucose. PpBGal42A exhibits significant degradative activity towards citrus pectin when combined with pectinase. Our findings suggest that PpBGal42A is a novel bifunctional enzyme that is active as a β-galactosidase and α-L-arabinopyranosidase. This study expands on the diversity of bifunctional enzymes and provides a potentially effective tool for the food industry.

Substrate recognition mode of a glycoside hydrolase family 42 β-galactosidase from Bifidobacterium longum subspecies infantis (BiBga42A) revealed by crystallographic and mutational analyses

Aim: Bifidobacterium longum subsp. infantis uses a glycoside hydrolase (GH) family 42 β-galactosidase (BiBga42A) for hydrolyzing lacto-N-tetraose (LNT), which is the most abundant core structure of human milk oligosaccharides (HMOs). As such, BiBga42A represents one of the pivotal enzymes underpinning the symbiosis between bifidobacteria and breastfed infants. Despite its importance, the structural basis underlying LNT hydrolysis by BiBga42A is not understood. Moreover, no substrate-complexed structures are available to date for GH42 family members. Methods: X-ray crystallography was used to determine the structures of BiBga42A in the apo- and liganded forms. The roles of the amino acid residues that were presumed to be involved in catalysis and substrate recognition were examined by a mutational study, in which kinetic parameters of each mutant were determined using 4-nitrophenyl-β-D-galactoside, lacto-N-biose I, LNT, and lacto-N-neotetraose (LNnT) as substrates. Conservation of those amino acid residues was examined among structure-determined GH42 β-galactosidases. Results: Crystal structures of the wild-type enzyme complexed with glycerol, the E160A/E318A double mutant complexed with galactose (Gal), and the E318S mutant complexed with LNT were determined at 1.7, 1.9, and 2.2 Å resolutions, respectively. The LNT molecule (excluding the Gal moiety at subsite +2) bound to the E318S mutant is recognized by an extensive hydrogen bond network and several hydrophobic interactions. The non-reducing end Gal moiety of LNT adopts a slightly distorted conformation and does not overlap well with the Gal molecule bound to the E160A/E318A mutant. Twelve of the sixteen amino acid residues responsible for LNT recognition and catalysis in BiBga42A are conserved among all homologs including β-1,6-1,3-galactosidase (BlGal42A) from Bifidobacterium animalis subsp. lactis. Conclusion: BlGal42A is active on 3-β-galactobiose similarly to BiBga42A but is inactive on LNT. Interestingly, we found that the entrance of the catalytic pocket of BlGal42A is narrower than that of BiBga42A and seems not easily accessible from the solvent side due to the presence of two bulky amino acid side chains. The specificity difference may reflect the structural difference between the two enzymes.

A novel salt-tolerant GH42 β-galactosidase with transglycosylation activity from deep-sea metagenome

β-Galactosidase is a widely adopted enzyme in the food and pharmaceutical industries. Metagenome techniques have the advantage of discovering novel functional genes, particularly potential genes from uncultivated microbes. In this study, a novel GH42 β-galactosidase isolated from a deep-sea metagenome was overexpressed in Escherichia coli BL21 (DE3) and purified by affinity chromatography. The optimal temperatures and pH of the enzyme for o-nitrophenyl-β-D-galactopyranoside (oNPG) and lactose were 40 ℃, 6.5 and 50 ℃, 7, respectively. The enzyme was stable at temperatures between 4 and 30 ℃ and within the pH range of 6-9. Moreover, it was highly tolerant to salt and inhibited by Zn²⁺ and Cu²⁺. The kinetic values of K_m and k_cat of the enzyme against oNPG were 1.1 mM and 57.8 s^-1, respectively. Furthermore, it showed hydrolysis and transglycosylation activity to lactose and the extra monosaccharides could improve the productivity of oligosaccharides. Overall, this recombinant β-galactosidase is a potential biocatalyst for the hydrolysis of milk lactose and synthesis of functional oligosaccharides.

A Novel Thermal-Activated β-Galactosidase from Bacillus aryabhattai GEL-09 for Lactose Hydrolysis in Milk

β-Galactosidase has been greatly used in the dairy industry. This study investigated a novel thermostable β-galactosidase (lacZBa) from Bacillus aryabhattai GEL-09 and evaluated the hydrolytic performance of this enzyme. Firstly, the lacZBa-encoding gene was cloned and overexpressed in Escherichia coli BL21(DE3). Phylogenetic analyses revealed that lacZBa belonged to the glycoside hydrolase family 42. Using SDS-PAGE, we determined that the molecular weight of lacZBa was ~75 kDa. Purified lacZBa exhibited a maximum activity at 45 °C, pH 6.0, and could be activated following incubation at 45 °C for several minutes. The half-life of lacZBa at 45 °C and 50 °C was 264 h and 36 h, respectively. While Co²⁺, Mn²⁺, Zn²⁺, Fe²⁺, Mg²⁺, and Ca²⁺ enhanced enzymatic activity, Cu²⁺ and ethylenediaminetetraacetic acid inhibited enzymatic activity. Moreover, lacZBa could hydrolyze lactose and oNPG with K_m values of 85.09 and 14.38 mM. Molecular docking results revealed that lacZBa efficiently recognized and catalyzed lactose. Additionally, the hydrolysis of lactose by lacZBa was studied in lactose solution and commercial milk. Lactose was completely hydrolyzed within 4 h with 8 U/mL of lacZBa at 45 °C. These results suggested that lacZBa identified in this study has potential applications in the dairy industry.

Engineering of a β-galactosidase from Bacillus coagulans to relieve product inhibition and improve hydrolysis performance

Most β-galactosidases reported are sensitive to the end product (galactose), making it the rate-limiting component for the efficient degradation of lactose through the enzymatic route. Therefore, there is ongoing interest in searching for galactose-tolerant β-galactosidases. In the present study, the predicted galactose-binding residues of β-galactosidase from Bacillus coagulans, which were determined by molecular docking, were selected for alanine substitution. The asparagine residue at position 148 (N148) is correlated with the reduction of galactose inhibition. Saturation mutations revealed that the N148C, N148D, N148S, and N148G mutants exhibited weaker galactose inhibition effects. The N148D mutant was used for lactose hydrolysis and exhibited a higher hydrolytic rate. Molecular dynamics revealed that the root mean square deviation and gyration radius of the N148D-galactose complex were higher than those of wild-type enzyme-galactose complex. In addition, the N148D mutant had a higher absolute binding free-energy value. All these factors may lead to a lower affinity between galactose and the mutant enzyme. The use of mutant enzyme may have potential value in lactose hydrolysis.

Cloning, expression, and bioinformatics analysis and characterization of a β-galactosidase from Bacillus coagulans T242

The activities of β-galactosidases from bacteria and molds are affected by temperature, pH, and other factors in the processing of dairy products, limiting their application, so it is necessary to find alternative lactases. In this study, the β-galactosidase gene from Bacillus coagulans T242 was cloned, co-expressed with a molecular chaperone in Escherichia coli BL21, and subjected to bioinformatic and kinetic analyses and lactase characterization. The results show that the enzyme is a novel thermostable neutral lactase with optimum hydrolytic activity at pH 6.8 and 50°C. The thermal stability and increased lactose hydrolysis activity of β-galactosidase in the presence of Ca²⁺ indicated its potential application in the dairy industry.

Structural features of cold-adapted dimeric GH2 β-D-galactosidase from Arthrobacter sp. 32cB

Crystal structures of cold-adapted β-d-galactosidase (EC 3.2.1.23) from the Antarctic bacterium Arthrobacter sp. 32cB (ArthβDG) have been determined in an unliganded form resulting from diffraction experiments conducted at 100 K (at resolution 1.8 Å) and at room temperature (at resolution 3.0 Å). A detailed comparison of those two structures of the same enzyme was performed in order to estimate differences in their molecular flexibility and rigidity and to study structural rationalization for the cold-adaptation of the investigated enzyme. Furthermore, a comparative analysis with structures of homologous enzymes from psychrophilic, mesophilic, and thermophilic sources has been discussed to elucidate the relationship between structure and cold-adaptation in a wider context. The performed studies confirm that the structure of cold-adapted ArthβDG maintains balance between molecular stability and structural flexibility, which can be observed independently on the temperature of conducted X-ray diffraction experiments. Obtained information about proper protein function under given conditions provide a guideline for rational engineering of proteins in terms of their temperature optimum and thermal stability.

β-Galactosidase from Exiguobacterium acetylicum: Cloning, expression, purification and characterization

The main goal of this work was to evaluate the performance of β-galactosidase from Exiguobacterium acetylicum MF03 in both hydrolysis and transgalactosylation reactions from different substrates. The enzyme gene was expressed in Escherichia coli BL21 (DE3), sequenced, and subjected to bioinformatic and kinetic assessment. Results showed that the enzyme was able to hydrolyze lactulose and o-nitrophenyl-β-d-galactopyranoside, but unable to hydrolyze lactose, o-nitrophenyl-β-d-glucopyranoside, butyl- and pentyl-β-d-galactosides. This unique and novel substrate specificity converts the E. acetylicum MF03 β-galactosidase into an ideal catalyst for the formulation of an enzymatic kit for lactulose quantification in thermally processed milk. This is because costly steps to eliminate glucose (resulting from hydrolysis of lactose when a customary β-galactosidase is used) can be avoided.

Choosing the Method of Crystallization to Obtain Optimal Results

Anyone who has ever attempted to crystallise a protein or other biological macromolecule has encountered at least one, if not all of the following scenarios: No crystals at all, tiny low quality crystals; phase separation; amorphous precipitate and the most frustrating; large, beautiful crystals that do not diffract at all. In this paper we review a number of simple ways to overcome such problems, which have worked well in our hands and in other laboratories. It brings together information that has been dispersed in various publications and lectures over the years and includes further information that has not been previously published.

Characterization of the regulation of a plant polysaccharide utilization operon and its role in biofilm formation in Bacillus subtilis

The soil bacterium Bacillus subtilis is often found in association with plants in the rhizosphere. Previously, plant polysaccharides have been shown to stimulate formation of root-associated multicellular communities, or biofilms, in this bacterium, yet the underlying mechanism is not fully understood. A five-gene gan operon (ganSPQAB) in B. subtilis has recently been shown to be involved in utilization of the plant-derived polysaccharide galactan. Despite these findings, molecular details about the regulation of the operon and the role of the operon in biofilm formation remain elusive. In this study, we performed comprehensive genetic analyses on the regulation of the gan operon. We show that this operon is regulated both by a LacI-like transcription repressor (GanR), which directly binds to pairs of inverted DNA repeats in the promoter region of the operon, and by the catabolite control protein A (CcpA). Derepression can be triggered by the presence of the inducer β-1,4-galactobiose, a hydrolysis product of galactan, or in situ when B. subtilis cells are associated with plant roots. In addition to the transcriptional regulation, the encoded ß-galactosidase GanA (by ganA), which hydrolyzes ß-1,4-galactobiose into galactose, is inhibited at the enzymatic level by the catalytic product galactose. Thus, the galactan utilization pathway is under complex regulation involving both positive and negative feedback mechanisms in B. subtilis. We discuss about the biological significance of such complex regulation as well as a hypothesis of biofilm induction by galactan via multiple mechanisms.

Biochemical and Structural Insights into a Novel Thermostable β-1,3-Galactosidase from Marinomonas sp. BSi20414

A novel β-1,3-galactosidase, designated as MaBGA (β-galactosidase from Marinomonas sp. BSi20414), was successfully purified to homogeneity from Marinomonas sp. BSi20414 isolated from Arctic sea ice by ammonium sulfate precipitation and anion exchange chromatography, resulting in an 8.12-fold increase in specific activity and 9.9% recovery in total activity. MaBGA displayed its maximum activity at pH 6.0 and 60 °C, and maintained at least 90% of its initial activity over the pH range of 5.0-8.0 after incubating for 1 h. It also exhibited considerable thermal stability, which retained 76% of its initial activity after incubating at 50 °C for 6 h. In contrast to other β-galactosidases, MaBGA displayed strict substrate specificity, not only for the glycosyl group, but also for the linkage type. To better understand the structure-function relationship, the encoding gene of MaBGA was obtained and subject to bioinformatics analysis. Multiple alignments and phylogenetic analysis revealed that MaBGA belonged to the glycoside hydrolase family 42 and had closer genetic relationships with thermophilic β-galactosidases of extremophiles. With the aid of homology modeling and molecular docking, we proposed a reasonable explanation for the linkage selectivity of MaBGA from a structural perspective. On account of the robust stability and 1,3-linkage selectivity, MaBGA would be a promising candidate in the biosynthesis of galacto-oligosaccharide with β1-3 linkage.

Structure-function relationships in Gan42B, an intracellular GH42 β-galactosidase from Geobacillus stearothermophilus

Geobacillus stearothermophilus T-6 is a Gram-positive thermophilic soil bacterium that contains a battery of degrading enzymes for the utilization of plant cell-wall polysaccharides, including xylan, arabinan and galactan. A 9.4 kb gene cluster has recently been characterized in G. stearothermophilus that encodes a number of galactan-utilization elements. A key enzyme of this degradation system is Gan42B, an intracellular GH42 β-galactosidase capable of hydrolyzing short β-1,4-galactosaccharides into galactose units, making it of high potential for various biotechnological applications. The Gan42B monomer is made up of 686 amino acids, and based on sequence homology it was suggested that Glu323 is the catalytic nucleophile and Glu159 is the catalytic acid/base. In the current study, the detailed three-dimensional structure of wild-type Gan42B (at 2.45 Å resolution) and its catalytic mutant E323A (at 2.50 Å resolution), as determined by X-ray crystallography, are reported. These structures demonstrate that the three-dimensional structure of the Gan42B monomer generally correlates with the overall fold observed for GH42 proteins, consisting of three main domains: an N-terminal TIM-barrel domain, a smaller mixed α/β domain, and the smallest all-β domain at the C-terminus. The two catalytic residues are located in the TIM-barrel domain in a pocket-like active site such that their carboxylic functional groups are about 5.3 Å from each other, consistent with a retaining mechanism. The crystal structure demonstrates that Gan42B is a homotrimer, resembling a flowerpot in general shape, in which each monomer interacts with the other two to form a cone-shaped tunnel cavity in the centre. The cavity is ∼35 Å at the wide opening and ∼5 Å at the small opening and ∼40 Å in length. The active sites are situated at the interfaces between the monomers, so that every two neighbouring monomers participate in the formation of each of the three active sites of the trimer. They are located near the small opening of the cone tunnel, all facing the centre of the cavity. The biological relevance of this trimeric structure is supported by independent results obtained from gel-permeation chromatography. These data and their comparison to the structural data of related GH42 enzymes are used for a more general discussion concerning structure-activity aspects in this GH family.

Genomic analysis of six new Geobacillus strains reveals highly conserved carbohydrate degradation architectures and strategies

In this work we report the whole genome sequences of six new Geobacillus xylanolytic strains along with the genomic analysis of their capability to degrade carbohydrates. The six sequenced Geobacillus strains described here have a range of GC contents from 43.9% to 52.5% and clade with named Geobacillus species throughout the entire genus. We have identified a ~200 kb unique super-cluster in all six strains, containing five to eight distinct carbohydrate degradation clusters in a single genomic region, a feature not seen in other genera. The Geobacillus strains rely on a small number of secreted enzymes located within distinct clusters for carbohydrate utilization, in contrast to most biomass-degrading organisms which contain numerous secreted enzymes located randomly throughout the genomes. All six strains are able to utilize fructose, arabinose, xylose, mannitol, gluconate, xylan, and α-1,6-glucosides. The gene clusters for utilization of these seven substrates have identical organization and the individual proteins have a high percent identity to their homologs. The strains show significant differences in their ability to utilize inositol, sucrose, lactose, α-mannosides, α-1,4-glucosides and arabinan.

Preliminary crystallographic analysis of Xyn52B2, a GH52 β-D-xylosidase from Geobacillus stearothermophilus T6

Geobacillus stearothermophilus T6 is a thermophilic bacterium that possesses an extensive hemicellulolytic system, including over 40 specific genes that are dedicated to this purpose. For the utilization of xylan, the bacterium uses an extracellular xylanase which degrades xylan to decorated xylo-oligomers that are imported into the cell. These oligomers are hydrolyzed by side-chain-cleaving enzymes such as arabinofuranosidases, acetylesterases and a glucuronidase, and finally by an intracellular xylanase and a number of β-xylosidases. One of these β-xylosidases is Xyn52B2, a GH52 enzyme that has already proved to be useful for various glycosynthesis applications. In addition to its demonstrated glycosynthase properties, interest in the structural aspects of Xyn52B2 stems from its special glycoside hydrolase family, GH52, the structures and mechanisms of which are only starting to be resolved. Here, the cloning, overexpression, purification and crystallization of Xyn52B2 are reported. The most suitable crystal form that has been obtained belonged to the orthorhombic P212121 space group, with average unit-cell parameters a = 97.7, b = 119.1, c = 242.3 Å. Several X-ray diffraction data sets have been collected from flash-cooled crystals of this form, including the wild-type enzyme (3.70 Å resolution), the E335G catalytic mutant (2.95 Å resolution), a potential mercury derivative (2.15 Å resolution) and a selenomethionine derivative (3.90 Å resolution). These data are currently being used for detailed three-dimensional structure determination of the Xyn52B2 protein.

Cloning, purification and preliminary crystallographic analysis of Ara127N, a GH127 β-L-arabinofuranosidase from Geobacillus stearothermophilus T6

The L-arabinan utilization system of Geobacillus stearothermophilus T6 is composed of five transcriptional units that are clustered within a 38 kb DNA segment. One of the transcriptional units contains 11 genes, the last gene of which (araN) encodes a protein, Ara127N, that belongs to the newly established GH127 family. Ara127N shares 44% sequence identity with the recently characterized HypBA1 protein from Bifidobacterium longum and thus is likely to function similarly as a β-L-arabinofuranosidase. β-L-Arabinofuranosidases are enzymes that hydrolyze β-L-arabinofuranoside linkages, the less common form of such linkages, a unique enzymatic activity that has been identified only recently. The interest in the structure and mode of action of Ara127N therefore stems from its special catalytic activity as well as its membership of the new GH127 family, the structure and mechanism of which are only starting to be resolved. Ara127N has recently been cloned, overexpressed, purified and crystallized. Two suitable crystal forms have been obtained: one (CTP form) belongs to the monoclinic space group P21, with unit-cell parameters a = 104.0, b = 131.2, c = 107.6 Å, β = 112.0°, and the other (RB form) belongs to the orthorhombic space group P212121, with unit-cell parameters a = 65.5, b = 118.1, c = 175.0 Å. A complete X-ray diffraction data set has been collected to 2.3 Å resolution from flash-cooled crystals of the wild-type enzyme (RB form) at -173°C using synchrotron radiation. A selenomethionine derivative of Ara127N has also been prepared and crystallized for multi-wavelength anomalous diffraction (MAD) experiments. Crystals of selenomethionine Ara127N appeared to be isomorphous to those of the wild type (CTP form) and enabled the measurement of a three-wavelength MAD diffraction data set at the selenium absorption edge. These data are currently being used for detailed three-dimensional structure determination of the Ara127N protein.

Preliminary crystallographic analysis of a double mutant of the acetyl xylo-oligosaccharide esterase Axe2 in its dimeric form

Xylans are polymeric sugars constituting a significant part of the plant cell wall. They are usually substituted with acetyl side groups attached at positions 2 or 3 of the xylose backbone units. Acetylxylan esterases are part of the hemicellulolytic system of many microorganisms which utilize plant biomass for growth. These enzymes hydrolyze the ester linkages of the xylan acetyl groups and thus improve the accessibility of main-chain-hydrolyzing enzymes and their ability to break down the sugar backbone units. The acetylxylan esterases are therefore critically important for those microorganisms and as such could be used for a wide range of biotechnological applications. The structure of an acetylxylan esterase (Axe2) isolated from the thermophilic bacterium Geobacillus stearothermophilus T6 has been determined, and it has been demonstrated that the wild-type enzyme is present as a unique torus-shaped octamer in the crystal and in solution. In order to understand the functional origin of this unique oligomeric structure, a series of rational noncatalytic, site-specific mutations have been made on Axe2. Some of these mutations led to a different dimeric form of the protein, which showed a significant reduction in catalytic activity. One of these double mutants, Axe2-Y184F-W190P, has recently been overexpressed, purified and crystallized. The best crystals obtained belonged to the orthorhombic space group P212121, with unit-cell parameters a = 71.1, b = 106.0, c = 378.6 Å. A full diffraction data set to 2.3 Å resolution has been collected from a flash-cooled crystal of this type at 100 K using synchrotron radiation. This data set is currently being used for the three-dimensional structure analysis of the Axe2-Y184F-W190P mutant in its dimeric form.

Purification, crystallization and preliminary crystallographic analysis of Gan1D, a GH1 6-phospho-β-galactosidase from Geobacillus stearothermophilus T1

Geobacillus stearothermophilus T1 is a Gram-positive thermophilic soil bacterium that contains an extensive system for the utilization of plant cell-wall polysaccharides, including xylan, arabinan and galactan. The bacterium uses a number of extracellular enzymes that break down the high-molecular-weight polysaccharides into short oligosaccharides, which enter the cell and are further hydrolyzed into sugar monomers by dedicated intracellular glycoside hydrolases. The interest in the biochemical characterization and structural analysis of these proteins originates mainly from the wide range of their potential biotechnological applications. Studying the different hemicellulolytic utilization systems in G. stearothermophilus T1, a new galactan-utilization gene cluster was recently identified, which encodes a number of proteins, one of which is a GH1 putative 6-phospho-β-galactosidase (Gan1D). Gan1D has recently been cloned, overexpressed, purified and crystallized as part of its comprehensive structure-function study. The best crystals obtained for this enzyme belonged to the triclinic space group P1, with average crystallographic unit-cell parameters of a = 67.0, b = 78.1, c = 92.1 Å, α = 102.4, β = 93.5, γ = 91.7°. A full diffraction data set to 1.33 Å resolution has been collected for the wild-type enzyme, as measured from flash-cooled crystals at 100 K, using synchrotron radiation. These data are currently being used for the detailed three-dimensional crystal structure analysis of Gan1D.