Publication Abstract from PubMed
Lipase LipA from Serratia marcescens is a 613-amino acid enzyme belonging to family I.3 of lipolytic enzymes that has an important biotechnological application in the production of a chiral precursor for the coronary vasodilator diltiazem. Like other family I.3 lipases, LipA is secreted by Gram-negative bacteria via a type I secretion system and possesses 13 copies of a calcium binding tandem repeat motif, GGXGXDXUX (U, hydrophobic amino acids), in the C-terminal part of the polypeptide chain. The 1.8-A crystal structure of LipA reveals a close relation to eukaryotic lipases, whereas family I.1 and I.2 enzymes appear to be more distantly related. Interestingly, the structure shows for the N-terminal lipase domain a variation on the canonical alpha/beta hydrolase fold in an open conformation, where the putative lid helix is anchored by a Ca(2+) ion essential for activity. Another novel feature observed in this lipase structure is the presence of a helical hairpin additional to the putative lid helix that exposes a hydrophobic surface to the aqueous medium and might function as an additional lid. The tandem repeats form two separated parallel beta-roll domains that pack tightly against each other. Variations of the consensus sequence of the tandem repeats within the second beta-roll result in an asymmetric Ca(2+) binding on only one side of the roll. The analysis of the properties of the beta-roll domains suggests an intramolecular chaperone function.
A calcium-gated lid and a large beta-roll sandwich are revealed by the crystal structure of extracellular lipase from Serratia marcescens.,Meier R, Drepper T, Svensson V, Jaeger KE, Baumann U J Biol Chem. 2007 Oct 26;282(43):31477-83. Epub 2007 Aug 28. PMID:17728256[1]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
