scholarly journals A metabolic regulon reveals early and late acting enzymes in neuroactive Lycopodium alkaloid biosynthesis

2021 ◽  
Vol 118 (24) ◽  
pp. e2102949118
Author(s):  
Ryan S. Nett ◽  
Yaereen Dho ◽  
Yun-Yee Low ◽  
Elizabeth S. Sattely
Keyword(s):  
Functional Characterization ◽  
Huperzine A ◽  
Piperidine Ring ◽  
Ring Cleavage ◽  
Chemical Transformations ◽  
Alkaloid Biosynthesis ◽  
Type Iii Polyketide Synthase ◽  
Type Iii ◽  
Lycopodium Alkaloids ◽  
Insight Into

Plants synthesize many diverse small molecules that affect function of the mammalian central nervous system, making them crucial sources of therapeutics for neurological disorders. A notable portion of neuroactive phytochemicals are lysine-derived alkaloids, but the mechanisms by which plants produce these compounds have remained largely unexplored. To better understand how plants synthesize these metabolites, we focused on biosynthesis of the Lycopodium alkaloids that are produced by club mosses, a clade of plants used traditionally as herbal medicines. Hundreds of Lycopodium alkaloids have been described, including huperzine A (HupA), an acetylcholine esterase inhibitor that has generated interest as a treatment for the symptoms of Alzheimer’s disease. Through combined metabolomic profiling and transcriptomics, we have identified a developmentally controlled set of biosynthetic genes, or potential regulon, for the Lycopodium alkaloids. The discovery of this putative regulon facilitated the biosynthetic reconstitution and functional characterization of six enzymes that act in the initiation and conclusion of HupA biosynthesis. This includes a type III polyketide synthase that catalyzes a crucial imine-polyketide condensation, as well as three Fe(II)/2-oxoglutarate–dependent dioxygenase (2OGD) enzymes that catalyze transformations (pyridone ring-forming desaturation, piperidine ring cleavage, and redox-neutral isomerization) within downstream HupA biosynthesis. Our results expand the diversity of known chemical transformations catalyzed by 2OGDs and provide mechanistic insight into the function of noncanonical type III PKS enzymes that generate plant alkaloid scaffolds. These data offer insight into the chemical logic of Lys-derived alkaloid biosynthesis and demonstrate the tightly coordinated coexpression of secondary metabolic genes for the biosynthesis of medicinal alkaloids.

scholarly journals Ectopic expression and functional characterization of type III polyketide synthase mutants from Emblica officinalis Gaertn

2016 ◽  
Vol 35 (10) ◽  
pp. 2077-2090 ◽  
Author(s):  
Girija Aiswarya ◽  
Vijayanathan Mallika ◽  
Luis A. J. Mur ◽  
Eppurathu Vasudevan Soniya
Keyword(s):  
Polyketide Synthase ◽  
Functional Characterization ◽  
Ectopic Expression ◽  
Emblica Officinalis ◽  
Type Iii Polyketide Synthase ◽  
Type Iii

scholarly journals Putative ligand binding sites of two functionally characterized bark beetle odorant receptors

BMC Biology ◽  
2021 ◽  
Vol 19 (1) ◽  
Author(s):  
Jothi K. Yuvaraj ◽  
Rebecca E. Roberts ◽  
Yonathan Sonntag ◽  
Xiao-Qing Hou ◽  
Ewald Grosse-Wilde ◽  
...  
Keyword(s):  
Ligand Binding ◽  
Bark Beetle ◽  
Pest Control ◽  
Binding Sites ◽  
Functional Characterization ◽  
Site Directed Mutagenesis ◽  
Odorant Receptors ◽  
Functional Evolution ◽  
General Importance ◽  
Insight Into

Abstract Background Bark beetles are major pests of conifer forests, and their behavior is primarily mediated via olfaction. Targeting the odorant receptors (ORs) may thus provide avenues towards improved pest control. Such an approach requires information on the function of ORs and their interactions with ligands, which is also essential for understanding the functional evolution of these receptors. Hence, we aimed to identify a high-quality complement of ORs from the destructive spruce bark beetle Ips typographus (Coleoptera, Curculionidae, Scolytinae) and analyze their antennal expression and phylogenetic relationships with ORs from other beetles. Using 68 biologically relevant test compounds, we next aimed to functionally characterize ecologically important ORs, using two systems for heterologous expression. Our final aim was to gain insight into the ligand-OR interaction of the functionally characterized ORs, using a combination of computational and experimental methods. Results We annotated 73 ORs from an antennal transcriptome of I. typographus and report the functional characterization of two ORs (ItypOR46 and ItypOR49), which are responsive to single enantiomers of the common bark beetle pheromone compounds ipsenol and ipsdienol, respectively. Their responses and antennal expression correlate with the specificities, localizations, and/or abundances of olfactory sensory neurons detecting these enantiomers. We use homology modeling and molecular docking to predict their binding sites. Our models reveal a likely binding cleft lined with residues that previously have been shown to affect the responses of insect ORs. Within this cleft, the active ligands are predicted to specifically interact with residues Tyr84 and Thr205 in ItypOR46. The suggested importance of these residues in the activation by ipsenol is experimentally supported through site-directed mutagenesis and functional testing, and hydrogen bonding appears key in pheromone binding. Conclusions The emerging insight into ligand binding in the two characterized ItypORs has a general importance for our understanding of the molecular and functional evolution of the insect OR gene family. Due to the ecological importance of the characterized receptors and widespread use of ipsenol and ipsdienol in bark beetle chemical communication, these ORs should be evaluated for their potential use in pest control and biosensors to detect bark beetle infestations.

scholarly journals Conformational Changes in IpaD fromShigella flexneriupon Binding Bile Salts Provide Insight into the Second Step of Type III Secretion

Biochemistry ◽  
2011 ◽  
Vol 50 (2) ◽  
pp. 172-180 ◽  
Author(s):  
Nicholas E. Dickenson ◽  
Lingling Zhang ◽  
Chelsea R. Epler ◽  
Philip R. Adam ◽  
Wendy L. Picking ◽  
...  
Keyword(s):  
Conformational Changes ◽  
Type Iii Secretion ◽  
Bile Salts ◽  
Second Step ◽  
Type Iii ◽  
Insight Into

scholarly journals The Serotype of Type Ia and III Group B Streptococci Is Determined by the Polymerase Gene within the Polycistronic Capsule Operon

2000 ◽  
Vol 182 (16) ◽  
pp. 4466-4477 ◽  
Author(s):  
Donald O. Chaffin ◽  
Stephen B. Beres ◽  
Harry H. Yim ◽  
Craig E. Rubens
Keyword(s):  
Capsular Polysaccharide ◽  
Single Gene ◽  
Functional Characterization ◽  
Neonatal Morbidity ◽  
Polymerase Gene ◽  
Chromosomal Dna ◽  
Group B Streptococci ◽  
Sequence Comparisons ◽  
Type Iii ◽  
Type Ia

ABSTRACT Streptococcus agalactiae is a primary cause of neonatal morbidity and mortality. Essential to the virulence of this pathogen is the production of a type-specific capsular polysaccharide (CPS) that enables the bacteria to evade host immune defenses. The identification, cloning, sequencing, and functional characterization of seven genes involved in type III capsule production have been previously reported. Here, we describe the cloning and sequencing of nine additional adjacent genes, cpsIIIFGHIJKL,neuIIIB, and neuIIIC. Sequence comparisons suggested that these genes are involved in sialic acid synthesis, pentasaccharide repeating unit formation, and oligosaccharide transport and polymerization. The type III CPS (cpsIII) locus was comprised of 16 genes within 15.5 kb of contiguous chromosomal DNA. Primer extension analysis and investigation of mRNA from mutants with polar insertions in their cpsIII loci supported the hypothesis that the operon is transcribed as a single polycistronic message. The translated cpsIII sequences were compared to those of the S. agalactiae cpsIa locus, and the primary difference between the operons was found to reside in cpsIIIH, the putative CPS polymerase gene. Expression of cpsIIIH in a type Ia strain resulted in suppression of CPS Ia synthesis and in production of a CPS which reacted with type III-specific polyclonal antibody. Likewise, expression of the putative type Ia polymerase gene in a type III strain reduced synthesis of type III CPS with production of a type Ia immunoreactive capsule. Based on the similar structures of the oligosaccharide repeating units of the type Ia and III capsules, our observations demonstrated that cpsIaH andcpsIIIH encoded the type Ia and III CPS polymerases, respectively. Additionally, these findings suggested that a single gene can confer serotype specificity in organisms that produce complex polysaccharides.

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