Pn. Rather et al., ANALYSIS OF THE AAC(3)-VIA GENE ENCODING A NOVEL 3-N-ACETYLTRANSFERASE, Antimicrobial agents and chemotherapy, 37(10), 1993, pp. 2074-2079
Biochemical analysis (G . A. Papanicolaou, R. S. Hare, R. Mierzwa, and
G. H. Miller, abstr. 152, Program Abstr. 29th Intersci. Conf. Antimic
rob. Agents Chemother., 1989) demonstrated the presence of a novel 3-N
-acetyltransferase in Enterobacter cloacae 88020217. This organism was
resistant to gentamicin, and the MIC of 2'-N-ethylnetilmicin for it w
as fourfold lower than that of 6'-N-ethylnetilmicin, a resistance patt
ern which suggested 2'-acetylating activity. However, high-pressure li
quid chromatography analysis demonstrated that the enzyme acetylated s
isomicin in the 3 position. We have cloned the structural gene for thi
s enzyme from a large (>70-kb) conjugative plasmid present in E. cloac
ae. Subcloning experiments have localized the aac(3)-VIa gene to a 2.1
-kb Sau3A fragment. The deduced AAC(3)-VIa protein showed 48% amino ac
id identity to the AAC(3)-IIa protein and 39% identity to the AAC(3)-V
II protein. Examination of the 5'-flanking sequences demonstrated that
the aac(3)-VIa gene was located 167 bp downstream of the aadA1 gene a
nd was present in an integron. In addition, the aac(3)-VIa gene is als
o downstream of a 59-base element often seen in an integron environmen
t. Primer extension analysis has identified a promoter for the aac(3)-
VIa gene downstream of both the aadA1 gene and a 59-base element.