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Updated: Aug 17, 2026

Functional Complementation Analysis (FCA): A Laboratory Exercise Designed and Implemented to Supplement the Teaching of Biochemical Pathways
Published on: June 24, 2016
fldA is an essential gene required in the 2-C-methyl-D-erythritol 4-phosphate pathway for isoprenoid biosynthesis
Kia-Joo Puan1, Hong Wang, Tohru Dairi
1Division of Rheumatology, Department of Internal Medicine and the Interdisciplinary Group in Immunology, University of Iowa, EMRB 340F, Iowa City, IA 52242, USA.
Abstract:
Although flavodoxin I is indispensable for Escherichia coli growth, the exact pathway(s) where flavodoxin I is essential has not been identified. We performed transposon mutagenesis of the flavodoxin I gene, fldA, in an E. coli strain that expressed mevalonate pathway enzymes and that had a point mutation in the lytB gene of the MEP pathway resulting in the accumulation of (E)-4-hydroxy-3-methylbutyl-2-enyl pyrophosphate (HMBPP). Disruption of fldA abrogated mevalonate-independent growth and dramatically decreased HMBPP levels. The fldA- mutant grew with mevalonate indicating that the essential role of flavodoxin I under aerobic conditions is in the MEP pathway. Growth was restored by fldA complementation. Since GcpE (which synthesizes HMBPP) and LytB are iron-sulfur enzymes that require a reducing system for their activity, we propose that flavodoxin is essential for GcpE and possibly LytB activity. Thus, the essential role for flavodoxin I in E. coli is in the MEP pathway for isoprenoid biosynthesis.
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