. 2019 Aug 14;32(4):e00007-19. doi: 10.1128/CMR.00007-19

TABLE 7.

Effect of specific amino acid substitutions and deletions at loops A and B on Qnr protection levels^a

Position(s) within TR	Change(s) in indicated Qnr causing a decrease in protection
Position(s) within TR	QnrA1	QnrB1	QnrC1	QnrS1
Loop A	ΔA₄₁–G₅₆
			ΔI₄₉–E₅₅
	ΔS₅₁–G₅₆
		Y₄₆A
		ΔY₄₆–Q₅₁
		S₅₀A
	ΔG₅₆/D	ΔG₅₃A/D/E		ΔG₅₆D/E

Loop B		N₁₀₃A
		M₁₀₄A
		ΔM₁₀₄–S₁₁₃
		I₁₀₅A		V₁₀₈A
		ΔT₁₀₆		S₁₀₉A
		ΔT₁₀₆–T₁₀₇
		ΔT₁₀₇
		ΔR₁₀₈
		ΔT₁₀₆–R₁₀₈
		ΔT₁₀₇-R₁₀₈
				M₁₁₂A
		W₁₁₀A		Y₁₁₃A
	F₁₁₄D	F₁₁₁A/D		F₁₁₄A
	C₁₁₅Y	C₁₁₂A/Y		C₁₁₅A/Y
		R₅₈H + R₈₇H + C₁₁₂Y^b + N₁₇₈Y
	S₁₁₆D	S₁₁₃A/D	S₁₁₆P	S₁₁₆A

Loops A + B		ΔY₄₆–Q₅₁ + ΔM₁₀₄–S₁₁₃

Amino acid substitutions are listed from top to bottom in the direction from the N to C termini. Changes in the same row are analogous to each other. The amino acids highlighted in boldface type are those leading to a full loss of Qnr activity and a subsequent lack of an effect on the final quinolone MICs. Note that cloning in different vectors may slightly affect the final full or partial loss of activity. The amino acid change is reported only when there is a positive or negative effect of at least 4-fold on the MIC of the quinolones described. Note that different studies have determined the Qnr effect on different quinolones. Loop A, amino acids 46 to 53 (QnrB) and amino acids 49 to 56 (QnrA, QnrC, QnrS, and QnrVC); loop B, amino acids 102 to 113 (QnrB); TR, tandem repeat; Δ, deletion (based on data from references 234, 235, 376, and 391 –394).

The amino acid change C₁₁₂Y is located in loop B.