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==Crystal structure of methyltransferase MpaG' in complex with SAH and DMMPA==
<StructureSection load='8xtg' size='340' side='right'caption='[[8xtg]], [[Resolution|resolution]] 2.00&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[8xtg]] is a 6 chain structure with sequence from [https://en.wikipedia.org/wiki/Penicillium_brevicompactum Penicillium brevicompactum]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=8XTG OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=8XTG FirstGlance]. <br>
</td></tr><tr id='method'><td class="sblockLbl"><b>[[Empirical_models|Method:]]</b></td><td class="sblockDat" id="methodDat">X-ray diffraction, [[Resolution|Resolution]] 2&#8491;</td></tr>
<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[https://proteopedia.org/fgij/fg.htm?mol=8xtg FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=8xtg OCA], [https://pdbe.org/8xtg PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=8xtg RCSB], [https://www.ebi.ac.uk/pdbsum/8xtg PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=8xtg ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/MPAG2_PENBR MPAG2_PENBR] O-methyltransferase; part of the gene cluster that mediates the biosynthesis of mycophenolic acid (MPA), the first isolated antibiotic natural product in the world obtained from a culture of Penicillium brevicompactum in 1893 (PubMed:25630520, PubMed:31209052). MpaG' methylates farnesyl-DHMP-3C (FDHMP-3C) to yield MFDHMP-3C (PubMed:25630520, PubMed:31209052). The first step of the pathway is the synthesis of 5-methylorsellinic acid (5MOA) by the cytosolic polyketide synthase mpaC. 5MOA is then converted to the phthalide compound 5,7-dihydroxy-4,6-dimethylphthalide (DHMP) by the endoplasmic reticulum-bound cytochrome P450 monooxygenase mpaDE. MpaDE first catalyzes hydroxylation of 5-MOA to 4,6-dihydroxy-2-(hydroxymethyl)-3-methylbenzoic acid (DHMB). MpaDE then acts as a lactone synthase that catalyzes the ring closure to convert DHMB into DHMP. The next step is the prenylation of DHMP by the Golgi apparatus-associated prenyltransferase mpaA to yield farnesyl-DHMP (FDHMP). The ER-bound oxygenase mpaB then mediates the oxidative cleavage the C19-C20 double bond in FDHMP to yield FDHMP-3C via a mycophenolic aldehyde intermediate. The O-methyltransferase mpaG catalyzes the methylation of FDHMP-3C to yield MFDHMP-3C. After the cytosolic methylation of FDHMP-3C, MFDHMP-3C enters into peroxisomes probably via free diffusion due to its low molecular weight. Upon a peroxisomal CoA ligation reaction, catalyzed by a beta-oxidation component enzyme acyl-CoA ligase ACL891, MFDHMP-3C-CoA would then be restricted to peroxisomes for the following beta-oxidation pathway steps. The peroxisomal beta-oxidation machinery than converts MFDHMP-3C-CoA into MPA_CoA, via a beta-oxidation chain-shortening process. Finally mpaH acts as a peroxisomal acyl-CoA hydrolase with high substrate specificity toward MPA-CoA to release the final product MPA (Probable) (PubMed:31209052).<ref>PMID:25630520</ref> <ref>PMID:31209052</ref> <ref>PMID:31209052</ref> 
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== Publication Abstract from PubMed ==
MpaG' is an S-adenosyl-L-methionine (SAM)-dependent methyltransferase involved in the compartmentalized biosynthesis of mycophenolic acid (MPA), a first-line immunosuppressive drug for organ transplantations and autoimmune diseases. MpaG' catalyzes the 5-O-methylation of three precursors in MPA biosynthesis including demethylmycophenolic acid (DMMPA), 4-farnesyl-3,5-dihydroxy-6-methylphthalide (FDHMP), and an intermediate containing three fewer carbon atoms compared to FDHMP (FDHMP-3C) with different catalytic efficiencies. Here, we report the crystal structures of S-adenosyl-L-homocysteine (SAH)/DMMPA-bound MpaG', SAH/FDHMP-3C-bound MpaG', and SAH/FDHMP-bound MpaG' to understand the catalytic mechanism of MpaG' and structural basis for its substrate flexibility. Structural and biochemical analyses reveal that MpaG' utilizes the catalytic dyad H306-E362 to deprotonate the C5 hydroxyl group of the substrates for the following methylation. The three substrates with differently modified farnesyl moieties are well accommodated in a large semi-open substrate binding pocket with the orientation of their phthalide moiety almost identical. Based on the structure-directed mutagenesis, a single mutant MpaG'(Q267A) is engineered with significantly improved catalytic efficiency for all three substrates. This study expands the mechanistic understanding and the pocket engineering strategy for O-methyltransferases involved in fungal natural product biosynthesis. Our research also highlights the potential of O-methyltransferases to modify diverse substrates by protein design and engineering.

Structural basis for substrate flexibility of the O-methyltransferase MpaG' involved in mycophenolic acid biosynthesis.,You C, Pan Y, Liu R, Li S, Feng Y Protein Sci. 2024 Sep;33(9):e5144. doi: 10.1002/pro.5144. PMID:39150221<ref>PMID:39150221</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
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== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Large Structures]]
[[Category: Penicillium brevicompactum]]
[[Category: Feng YG]]
[[Category: Li SY]]
[[Category: Pan YJ]]
[[Category: You C]]