Structural and Functional Analysis of Latex Clearing Protein (Lcp) Provides Insight into the Enzymatic Cleavage of Rubber

Latex clearing proteins (Lcps) are rubber oxygenases that catalyse the extracellular cleavage of poly (cis-1,4-isoprene) by Gram-positive rubber degrading bacteria. Lcp of Streptomyces sp. K30 (Lcp(K30)) is a b-type cytochrome and acts as an endo-type dioxygenase producing C(20) and higher oligo-isoprenoids that differ in the number of isoprene units but have the same terminal functions, CHO-CH(2)– and –CH(2)-COCH(3). Our analysis of the Lcp(K30) structure revealed a 3/3 globin fold with additional domains at the N- and C-termini and similarities to globin-coupled sensor proteins. The haem group of Lcp(K30) is ligated to the polypeptide by a proximal histidine (His198) and by a lysine residue (Lys167) as the distal axial ligand. The comparison of Lcp(K30) structures in a closed and in an open state as well as spectroscopic and biochemical analysis of wild type and Lcp(K30) muteins provided insights into the action of the enzyme during catalysis.