High-resolution structures of complexes of plant S-adenosyl-L-homocysteine hydrolase (Lupinus luteus).
Summary of "High-resolution structures of complexes of plant S-adenosyl-L-homocysteine hydrolase (Lupinus luteus)."
S-Adenosyl-L-homocysteine hydrolase (SAHase) catalyzes the reversible breakdown of S-adenosyl-L-homocysteine (SAH) to adenosine and homocysteine. SAH is formed in methylation reactions that utilize S-adenosyl-L-methionine (SAM) as a methyl donor. By removing the SAH byproduct, SAHase serves as a major regulator of SAM-dependent biological methylation reactions. Here, the first crystal structure of SAHase of plant origin, that from the legume yellow lupin (LlSAHase), is presented. Structures have been determined at high resolution for three complexes of the enzyme: those with a reaction byproduct/substrate (adenosine), with its nonoxidizable analog (cordycepin) and with a product of inhibitor cleavage (adenine). In all three cases the enzyme has a closed conformation. A sodium cation is found near the active site, coordinated by residues from a conserved loop that hinges domain movement upon reactant binding. An insertion segment that is present in all plant SAHases is located near a substrate-pocket access channel and participates in its formation. In contrast to mammalian and bacterial SAHases, the channel is open when adenosine or cordycepin is bound and is closed in the adenine complex. In contrast to SAHases from other organisms, which are active as tetramers, the plant enzyme functions as a homodimer in solution.
Affiliation
Center for Biocrystallographic Research, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, Poland.
Journal Details
This article was published in the following journal.
Name: Acta crystallographica. Section D, Biological crystallography
ISSN: 1399-0047
Pages: 218-31
Links
- PubMed Source: http://www.ncbi.nlm.nih.gov/pubmed/22349223
- DOI: http://dx.doi.org/10.1107/S0907444911055090
Medical and Biotech [MESH] Definitions
Phenylethanolamine N-methyltransferase
A methyltransferase that catalyzes the reaction of S-adenosyl-L-methionine and phenylethanolamine to yield S-adenosyl-L-homocysteine and N-methylphenylethanolamine. It can act on various phenylethanolamines and converts norepinephrine into epinephrine. (From Enzyme Nomenclature, 1992) EC 2.1.1.28.
Site-specific Dna-methyltransferase (adenine-specific)
An enzyme responsible for producing a species-characteristic methylation pattern on adenine residues in a specific short base sequence in the host cell DNA. The enzyme catalyzes the methylation of DNA adenine in the presence of S-adenosyl-L-methionine to form DNA containing 6-methylaminopurine and S-adenosyl-L-homocysteine. EC 2.1.1.72.
Homocysteine S-methyltransferase
An enzyme that catalyzes the demethylation of L-homocysteine to L-METHIONINE.
5-methyltetrahydrofolate-homocysteine S-methyltransferase
An enzyme that catalyzes the formation of methionine by transfer of a methyl group from 5-methyltetrahydrofolate to homocysteine. It requires a cobamide coenzyme. The enzyme can act on mono- or triglutamate derivatives. EC 2.1.1.13.
Betaine-homocysteine S-methyltransferase
A ZINC metalloenzyme that catalyzes the transfer of a methyl group from BETAINE to HOMOCYSTEINE to produce dimethylglycine and METHIONINE, respectively. This enzyme is a member of a family of ZINC-dependent METHYLTRANSFERASES that use THIOLS or selenols as methyl acceptors.
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