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Publication Abstract from PubMed

The SCP2-thiolase (type-1) functions in the vertebrate peroxisomal, bile acid synthesis pathway, converting 24-keto-THC-CoA and CoA into choloyl-CoA and propionyl-CoA. This conversion concerns the beta-oxidation chain shortening of the steroid fatty acyl moiety of 24-keto-THC-CoA. This class of dimeric thiolases has previously been poorly characterized. High resolution crystal structures of the zebrafish SCP2-thiolase (type-1) now reveal an open catalytic site, shaped by residues of both subunits. The structure of its non-dimerised monomeric form has also been captured in the obtained crystals. Four loops at the dimer interface adopt very different conformations in the monomeric form. These loops also shape the active site and their structural changes explain why a competent active site is not present in the monomeric form. Native mass spectrometry studies confirm that the zebrafish SCP2-thiolase (type-1) as well as its human homologue are weak transient dimers in solution. The crystallographic binding studies reveal the mode of binding of CoA and octanoyl-CoA in the active site, highlighting the conserved geometry of the nucleophilic cysteine, the catalytic acid/base cysteine and the two oxyanion holes. The dimer interface of SCP2-thiolase (type-1) is equally extensive as in other thiolase dimers, however it is more polar than any of the corresponding interfaces, which correlates with the notion that the enzyme forms a weak transient dimer. The structure comparison of the monomeric and dimeric forms suggests functional relevance of this property. These comparisons provide also insight into the structural rearrangements that occur when the folded inactive monomers assemble into the mature dimer.

The peroxisomal zebrafish SCP2-thiolase (type-1) is a weak transient dimer as revealed by crystal structures and native mass spectrometry.,Kiema TR, Thapa CJ, Laitaoja M, Schmitz W, Maksimainen MM, Fukao T, Rouvinen J, Janis J, Wierenga RK Biochem J. 2018 Dec 20. pii: BCJ20180788. doi: 10.1042/BCJ20180788. PMID:30573650^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.