Skip to content
Login Register

#structural genes

3 public questions tagged with this topic.

Gene regulation in Prokaryotes

Ara operon structural genes are

Arabinose structural genes are organized as contiguous araBAD cluster transcribed as single polycistronic messenger from PBAD promoter under dual control. araB encodes ribulokinase enzyme phosphorylating L-ribulose using ATP producing ribulose-5-phosphate; araA encodes L-arabinose isomerase converting L-arabinose aldose to L-ribulose ketose; araD encodes L-ribulose-5-phosphate 4-epimerase generating D-xylulose-5-phosphate which enters pentose phosphate pathway for energy and biosynthesis. Together three enzymes divert abundant plant-derived pentose sugar into central carbon metabolism. araC regulatory gene transcribed divergently from same intergenic control region forms separate transcription unit with autoregulated PC promoter.

Ref: PMC Transcriptional Control L-Arabinose Operon – structural genes araB A D metabolize arabinose via PBAD promoter.

View Details
Gene regulation in Prokaryotes

Structural genes of trp operon include

Structural region trpEDCBA spans approximately seven kilobases encoding catalytic subunits for chorismate to L-tryptophan conversion. trpE and trpD together encode anthranilate synthase component I and component II catalyzing chorismate amination with glutamine; trpD also provides anthranilate phosphoribosyltransferase activity; trpC encodes bifunctional protein with N-terminal indole-3-glycerol phosphate synthase and C-terminal isomerase; trpB and trpA form heterotetrameric tryptophan synthase alpha2beta2 complex converting indole-glycerol phosphate plus serine to tryptophan. Polycistronic arrangement from single promoter ensures coordinated equimolar synthesis of sequential pathway enzymes from one messenger RNA for efficient metabolic flux.

Ref: Wikipedia trp operon – structural genes trpE D C B A encode enzymes for tryptophan synthesis.

View Details
Lac Operon

Structural genes of lac operon are

Jacob-Monod lac system organizes regulatory and coding modules separately into distinct genetic elements. Structural segment responsible for lactose utilization consists of three tandem genes lacZ, lacY, lacA cotranscribed as single polycistronic mRNA from promoter P downstream of operator site. Each cistron possesses independent Shine-Dalgarno site allowing separate translational initiation. Regulatory locus lacI resides upstream, expressed separately from its own promoter, producing trans-acting repressor that controls operator, not part of operon transcript itself. lacP and lacO designation combine promoter-operator, CAP site is upstream activator site, and trp genes belong to distinct repressible operon regulating tryptophan synthesis.

Ref: Alberts Fig 7-37 Lac operon structure lacZYA structural genes; NCBI Operon maps lacZ lacY lacA encode structural proteins

View Details