Gingipains — MFDS Part 1 MCQ

Instant feedback + full explanation. One question, done properly.

HardMicrobiologyGingipainsMFDS Part 1

An isogenic Porphyromonas gingivalis mutant retains extracellular proteolytic cleavage at Arg-X peptide bonds but has lost cleavage at Lys-X peptide bonds. Which locus has most likely been inactivated?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: B — kgp

The correct answer is **A, kgp**. This locus encodes Kgp, the lysine-specific gingipain responsible for extracellular cleavage at Lys-X peptide bonds. Gingipains are major cysteine-protease virulence factors of P. gingivalis and contribute to host-protein degradation and immune dysregulation. The retained Arg-X cleavage excludes rgpA and rgpB, which encode the two arginine-specific gingipains, RgpA and RgpB. The ppAD locus encodes peptidylarginine deiminase, which citrullinates arginine residues rather than producing Lys-X-specific proteolysis. fimA encodes a major fimbrial protein involved principally in adhesion and colonisation, not gingipain activity.

Reference: Aduse-Opoku J et al. Generation of lys-gingipain protease activity in Porphyromonas gingivalis W50 is independent of Arg-gingipain protease activities. Microbiology. 2000;146:1933–1940. https://pubmed.ncbi.nlm.nih.gov/10931897/