Fujimura S, Tokue Y, Takahashi H, Kobayashi T, Gomi K, Abe T, Nukiwa T, Watanabe A
Department of Respiratory Oncology and Molecular Medicine, Institute of Development, Aging and Cancer, Tohoku University, Sendai, Japan.
FEMS Microbiol Lett. 2000 Sep 15;190(2):299-303. doi: 10.1111/j.1574-6968.2000.tb09302.x.
An aminoglycoside-modifying enzyme in arbekacin-resistant methicillin-resistant Staphylococcus aureus (MRSA), exhibiting 4'''-N-acetylation, was examined. Although the MRSA strain with AAC(4''') had no AAC(6')-APH(2") activity, a DNA fragment of the AAC(6')-APH(2") gene was amplified by PCR and the purified N-terminal 30-amino acid sequence of this AAC(4''') was identical to AAC(6')-APH(2"). Direct DNA sequencing of this 'silent' AAC(6')-APH(2") gene revealed a single point mutation leading to a substitution of Gly for Asp80, through which the secondary structure is affected. A change in protein conformation could lead to a cleavage and a change of the enzymatic activity. We propose a new aminoglycoside-resistance mediated by AAC(4''') is caused by a mutation-modified AAC(6')-APH(2").
对耐阿贝卡星的耐甲氧西林金黄色葡萄球菌（MRSA）中一种表现出4'''-N-乙酰化作用的氨基糖苷修饰酶进行了研究。尽管携带AAC(4''')的MRSA菌株没有AAC(6')-APH(2")活性，但通过PCR扩增出了AAC(6')-APH(2")基因的DNA片段，并且该AAC(4''')纯化后的N端30个氨基酸序列与AAC(6')-APH(2")相同。对这个“沉默”的AAC(6')-APH(2")基因进行直接DNA测序，发现一个单点突变导致Asp80被Gly取代，由此影响了二级结构。蛋白质构象的改变可能导致酶的裂解和活性变化。我们提出由AAC(4''')介导的一种新的氨基糖苷耐药性是由突变修饰的AAC(6')-APH(2")引起的。
