Question

Which of the following bacteriocins is different from others?

• A. Lacticin F
• B. Lacticin B
• C. Lacticin 481
• D. Lactococcin A

Hint:

Bacteriocin Classes:
Class I (Lantibiotics Lanthionine-containing) = Nisin, Lacticin 481, Lacticin 3147, Lacticin F, Lacticin B.
Class II (Non-Lantibiotics) = LACTOCOCCIN A, Pediocin PA-1, Enterocin A.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Classification of lactic acid bacterial bacteriocins: Class I lantibiotics contain modified thioether amino acids (lanthionine, $eta$-methyllanthionine), whereas Class II bacteriocins (Lactococcin A) are unmodified non-lanthionine-containing peptides.
Key Formula or Approach:
\[ \text{Bacteriocin Classification: } \underbrace{\text{Lacticin 481, Lacticin F, Lacticin B}}_{\text{Class I Lantibiotics (Lanthionine-containing)}} \quad \longleftrightarrow \quad \underbrace{\mathbf{Lactococcin \text{ } A}}_{\mathbf{Class \text{ } II \text{ Non-Lantibiotic Peptide}}} \]

Step 2: Detailed Explanation:
In molecular bacteriocinology and classification of antimicrobial peptides produced by LAB:
1. Class I Bacteriocins (Lantibiotics): Small ($< 5\text{ kDa}$) post-translationally modified peptides containing unusual thioether amino acids Lanthionine and $\beta$-Methyllanthionine with dehydro-residues (e.g., Nisin, Lacticin 481, Lacticin F, Lacticin B, Lacticin 3147).
2. Class II Bacteriocins (Non-Lantibiotics) (D): Small ($< 10\text{ kDa}$), heat-stable, unmodified linear peptides containing NO lanthionine residues. Lactococcin A (produced by Lactococcus lactis subsp. cremoris) is the classic prototypical Class IIa/IIc non-lantibiotic pore-forming bacteriocin.
- Therefore, Lactococcin A belongs to a fundamentally different structural and biosynthetic class.

Step 3: Final Answer:
Thus, Lactococcin A is different from others, corresponding to option (D).