Letunic et al. (2017) Nucleic Acids Res doi: 10.1093/nar/gkx922
Letunic et al. (2020) Nucleic Acids Res doi: 10.1093/nar/gkaa937

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BetaGal_dom2 Beta-galactosidase, domain 2

SMART accession number:	SM01029
Description:	This is the second domain of the five-domain beta-galactosidase enzyme that altogether catalyses the hydrolysis of beta(1-3) and beta(1-4) galactosyl bonds in oligosaccharides as well as the inverse reaction of enzymatic condensation and trans-glycosylation. This domain is made up of 16 antiparallel beta-strands and an alpha-helix at its C terminus. The fold of this domain appears to be unique. In addition, the last seven strands of the domain form a subdomain with an immunoglobulin-like (I-type Ig) fold in which the first strand is divided between the two beta-sheets. In penicillin spp this strand is interrupted by a 12-residue insertion which forms an additional edge-strand to the second beta-sheet of the sub-domain. The remainder of the second domain forms a series of beta-hairpins at its N terminus, four strands of which are contiguous with part of the Ig-like sub-domain, forming in total a seven-stranded antiparallel beta-sheet. This domain is associated with family Glyco_hydro_35, which is N-terminal to it, but itself has no metazoan members.
Interpro abstract (IPR018954):	This entry represents the second domain of the five-domain beta-galactosidase enzyme that altogether catalyses the hydrolysis of beta(1-3) and beta(1-4) galactosyl bonds in oligosaccharides as well as the inverse reaction of enzymatic condensation and trans-glycosylation. This domain is made up of 16 antiparallel beta-strands and an alpha-helix at its C terminus. The fold of this domain appears to be unique. In addition, the last seven strands of the domain form a subdomain with an immunoglobulin-like (I-type Ig) fold in which the first strand is divided between the two beta-sheets. In penicillin spp this strand is interrupted by a 12-residue insertion which forms an additional edge-strand to the second beta-sheet of the sub-domain. The remainder of the second domain forms a series of beta-hairpins at its N terminus, four strands of which are contiguous with part of the Ig-like sub-domain, forming in total a seven-stranded antiparallel beta-sheet.
Family alignment:	View or CHROMA formatHMM/Web logoCLUSTALW formatMSF formatFASTA formatPIR format

There are 354 BetaGal_dom2 domains in 353 proteins in SMART's nrdb database.

Click on the following links for more information.

• Evolution (species in which this domain is found)

• Taxonomic distribution of proteins containing BetaGal_dom2 domain.

  This tree includes only several representative species. The complete taxonomic breakdown of all proteins with BetaGal_dom2 domain is also avaliable.

  Click on the protein counts, or double click on taxonomic names to display all proteins containing BetaGal_dom2 domain in the selected taxonomic class.

• Literature (relevant references for this domain)

• Primary literature is listed below; Automatically-derived, secondary literature is also avaliable.

  • Rojas AL et al.
  • Crystal structures of beta-galactosidase from Penicillium sp. and itscomplex with galactose.
  • J Mol Biol. 2004; 343: 1281-92
  • Display abstract

  • Beta-galactosidases catalyze the hydrolysis of beta(1-3) and beta(1-4)galactosyl bonds in oligosaccharides as well as the inverse reaction ofenzymatic condensation and transglycosylation. Here we report thecrystallographic structures of Penicillium sp. beta-galactosidase and itscomplex with galactose solved by the SIRAS quick cryo-soaking technique at1.90 A and 2.10 A resolution, respectively. The amino acid sequence ofthis 120 kDa protein was first assigned putatively on the basis ofinspection of the experimental electron density maps and then determinedby nucleotide sequence analysis. Primary structure alignments reveal thatPenicillium sp. beta-galactosidase belongs to family 35 of glycosylhydrolases (GHF-35). This model is the first 3D structure for a member ofGHF-35. Five distinct domains which comprise the structure are assembledin a way previously unobserved for beta-galactosidases. Superposition ofthis complex with other beta-galactosidase complexes from severalhydrolase families allowed the identification of residue Glu200 as theproton donor and residue Glu299 as the nucleophile involved in catalysis.Penicillium sp. beta-galactosidase is a glycoprotein containing sevenN-linked oligosaccharide chains and is the only structure of aglycosylated beta-galactosidase described to date.

• Structure (3D structures containing this domain)

• 3D Structures of BetaGal_dom2 domains in PDB

  PDB code	Main view	Title
  1tg7		Native structure of beta-galactosidase from Penicillium sp.
  1xc6		Native Structure Of Beta-Galactosidase from Penicillium sp. in complex with Galactose
  3og2		Native crystal structure of Trichoderma reesei beta-galactosidase
  3ogr		Complex structure of beta-galactosidase from Trichoderma reesei with galactose
  3ogs		Complex structure of beta-galactosidase from Trichoderma reesei with IPTG
  3ogv		Complex structure of beta-galactosidase from Trichoderma reesei with PETG
  4iug		Crystal structure of beta-galactosidase from Aspergillus oryzae in complex with galactose

• Links (links to other resources describing this domain)

• INTERPRO	IPR018954
  PFAM	BetaGal_dom2

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