4B0N

Crystal structure of PKS-I from the brown algae Ectocarpus siliculosus

Summary for 4B0N

• Entry DOI: 10.2210/pdb4b0n/pdb
• Descriptor: POLYKETIDE SYNTHASE III, MALONIC ACID, ARACHIDONIC ACID, ... (4 entities in total)
• Functional Keywords: transferase, polyphenol biosynthesis, arachidonyl group
• Biological source: ECTOCARPUS SILICULOSUS (BROWN ALGAE)
• Total number of polymer chains: 2
• Total formula weight: 89835.46

Authors

Leroux, C.,Meslet-Cladiere, L.,Delage, L.,Goulitquer, S.,Leblanc, C.,Ar Gall, E.,Stiger-Pouvreau, V.,Potin, P.,Czjzek, M. (deposition date: 2012-07-03, release date: 2013-07-10, Last modification date: 2024-10-16)

Primary citation

Meslet-Cladiere, L.,Delage, L.,J-J Leroux, C.,Goulitquer, S.,Leblanc, C.,Creis, E.,Gall, E.A.,Stiger-Pouvreau, V.,Czjzek, M.,Potin, P.
Structure/Function Analysis of a Type III Polyketide Synthase in the Brown Alga Ectocarpus Siliculosus Reveals a Biochemical Pathway in Phlorotannin Monomer Biosynthesis.
Plant Cell, 25:3089-, 2013

PubMed Abstract: Brown algal phlorotannins are structural analogs of condensed tannins in terrestrial plants and, like plant phenols, they have numerous biological functions. Despite their importance in brown algae, phlorotannin biosynthetic pathways have been poorly characterized at the molecular level. We found that a predicted type III polyketide synthase in the genome of the brown alga Ectocarpus siliculosus, PKS1, catalyzes a major step in the biosynthetic pathway of phlorotannins (i.e., the synthesis of phloroglucinol monomers from malonyl-CoA). The crystal structure of PKS1 at 2.85-Å resolution provided a good quality electron density map showing a modified Cys residue, likely connected to a long chain acyl group. An additional pocket not found in other known type III PKSs contains a reaction product that might correspond to a phloroglucinol precursor. In vivo, we also found a positive correlation between the phloroglucinol content and the PKS III gene expression level in cells of a strain of Ectocarpus adapted to freshwater during its reacclimation to seawater. The evolution of the type III PKS gene family in Stramenopiles suggests a lateral gene transfer event from an actinobacterium.

PubMed: 23983220
DOI: 10.1105/TPC.113.111336

Experimental method

X-RAY DIFFRACTION (2.85 Å)