| Structural highlights
Function
[GLFT2_MYCTU] Involved in the polymerization of the arabinogalactan (AG) region of the mycolylarabinogalactan-peptidoglycan (mAGP) complex, an essential component the mycobacteria cell wall, through successively beta-D-(1->5) and beta-D-(1->6)-galactofuranosyltransferases activities. It transfers the galactofuranosyl (Galf) unit from UDP-galactofuranosyl (UDP-Galf) onto the galactofuranosyl-rhamnosyl-GlcNAc-pyrophosphoryl-undecaprenyl (Galf-Rha-GlcNAc-PP-C55), yielding polygalactofuranosyl-rhamnosyl-GlcNAc-pyrophosphoryl-undecaprenyl ((Galf)x-Rha-GlcNAc-PP-C55). It is able to transfer Galf onto beta-D-(1->5) or beta-D-(1->6) linked acceptor, but has a stronger affinity for beta-D-(1->6) acceptor.[1] [2] [3] [4] [5] [6]
Publication Abstract from PubMed
Biosynthesis of the mycobacterial cell wall relies on the activities of many enzymes, including several glycosyltransferases (GTs). The polymerizing galactofuranosyltransferase GlfT2 (Rv3808c) synthesizes the bulk of the galactan portion of the mycolyl-arabinogalactan complex, which is the largest component of the mycobacterial cell wall. We used x-ray crystallography to determine the 2.45-A resolution crystal structure of GlfT2, revealing an unprecedented multidomain structure in which an N-terminal beta-barrel domain and two primarily alpha-helical C-terminal domains flank a central GT-A domain. The kidney-shaped protomers assemble into a C(4)-symmetric homotetramer with an open central core and a surface containing exposed hydrophobic and positively charged residues likely involved with membrane binding. The structure of a 3.1-A resolution complex of GlfT2 with UDP reveals a distinctive mode of nucleotide recognition. In addition, models for the binding of UDP-galactofuranose and acceptor substrates in combination with site-directed mutagenesis and kinetic studies suggest a mechanism that explains the unique ability of GlfT2 to generate alternating beta-(1-->5) and beta-(1-->6) glycosidic linkages using a single active site. The topology imposed by docking a tetrameric assembly onto a membrane bilayer also provides novel insights into aspects of processivity and chain length regulation in this and possibly other polymerizing GTs.
Tetrameric Structure of the GlfT2 Galactofuranosyltransferase Reveals a Scaffold for the Assembly of Mycobacterial Arabinogalactan.,Wheatley RW, Zheng RB, Richards MR, Lowary TL, Ng KK J Biol Chem. 2012 Aug 10;287(33):28132-43. Epub 2012 Jun 15. PMID:22707726[7]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Mikusova K, Yagi T, Stern R, McNeil MR, Besra GS, Crick DC, Brennan PJ. Biosynthesis of the galactan component of the mycobacterial cell wall. J Biol Chem. 2000 Oct 27;275(43):33890-7. PMID:10934214 doi:http://dx.doi.org/10.1074/jbc.M006875200
- ↑ Kremer L, Dover LG, Morehouse C, Hitchin P, Everett M, Morris HR, Dell A, Brennan PJ, McNeil MR, Flaherty C, Duncan K, Besra GS. Galactan biosynthesis in Mycobacterium tuberculosis. Identification of a bifunctional UDP-galactofuranosyltransferase. J Biol Chem. 2001 Jul 13;276(28):26430-40. Epub 2001 Apr 13. PMID:11304545 doi:http://dx.doi.org/10.1074/jbc.M102022200
- ↑ Rose NL, Completo GC, Lin SJ, McNeil M, Palcic MM, Lowary TL. Expression, purification, and characterization of a galactofuranosyltransferase involved in Mycobacterium tuberculosis arabinogalactan biosynthesis. J Am Chem Soc. 2006 May 24;128(20):6721-9. PMID:16704275 doi:http://dx.doi.org/10.1021/ja058254d
- ↑ Belanova M, Dianiskova P, Brennan PJ, Completo GC, Rose NL, Lowary TL, Mikusova K. Galactosyl transferases in mycobacterial cell wall synthesis. J Bacteriol. 2008 Feb;190(3):1141-5. Epub 2007 Nov 30. PMID:18055597 doi:http://dx.doi.org/10.1128/JB.01326-07
- ↑ Rose NL, Zheng RB, Pearcey J, Zhou R, Completo GC, Lowary TL. Development of a coupled spectrophotometric assay for GlfT2, a bifunctional mycobacterial galactofuranosyltransferase. Carbohydr Res. 2008 Aug 11;343(12):2130-9. doi: 10.1016/j.carres.2008.03.023., Epub 2008 Mar 24. PMID:18423586 doi:http://dx.doi.org/10.1016/j.carres.2008.03.023
- ↑ May JF, Splain RA, Brotschi C, Kiessling LL. A tethering mechanism for length control in a processive carbohydrate polymerization. Proc Natl Acad Sci U S A. 2009 Jul 21;106(29):11851-6. doi:, 10.1073/pnas.0901407106. Epub 2009 Jul 1. PMID:19571009 doi:http://dx.doi.org/10.1073/pnas.0901407106
- ↑ Wheatley RW, Zheng RB, Richards MR, Lowary TL, Ng KK. Tetrameric Structure of the GlfT2 Galactofuranosyltransferase Reveals a Scaffold for the Assembly of Mycobacterial Arabinogalactan. J Biol Chem. 2012 Aug 10;287(33):28132-43. Epub 2012 Jun 15. PMID:22707726 doi:10.1074/jbc.M112.347484
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