Miyazaki M, Matsumura F, Beeman R W
Department of Environmental Toxicology, University of California, Davis 95616, USA.
Comp Biochem Physiol B Biochem Mol Biol. 1995 Jul;111(3):399-406. doi: 10.1016/0305-0491(95)00007-u.
Using polymerase chain reactions (PCR) on cDNA, the DNA sequence of a membrane spanning region of a GABA receptor of the red flour beetle, Tribolium castaneum was identified. The deduced amino acid sequence indicates that its basic structure is similar to the GABA receptor of Rdl type subunits of Drosophila melanogaster and of Blattella germanica. Particularly conserved are M1, M2 and M3 segments. Within this 146 amino acid stretch, the GABA receptor from the red flour beetle differed from corresponding ones from Drosophila and Rdl subunit of B. germanica by 12 and eight amino acids, respectively. By using an identical approach, the corresponding DNA region was sequenced from the cDNA of a cyclodiene-resistant strain of T. castaneum. While two points of mutation were found only one mutation in DNA was found to result in an amino acid shift. The site of mutation was at the 5th amino acid of the M2 cylinder where G to T conversion of the GCT codon resulted in a conversion of alanine to serine. This is qualitatively the same mutational switch of alanine to serine in resistant strains previously reported to have occurred in cyclodiene-resistant Drosophila melanogaster, Aedes aegypti and Blattella germanica, indicating that this amino acid change is the likely cause for evolution of the nerve insensitive type of resistance to cyclodiene insecticides.
通过对cDNA进行聚合酶链反应（PCR），鉴定出了赤拟谷盗（Tribolium castaneum）GABA受体跨膜区域的DNA序列。推导的氨基酸序列表明，其基本结构与黑腹果蝇（Drosophila melanogaster）和德国小蠊（Blattella germanica）Rdl型亚基的GABA受体相似。特别保守的是M1、M2和M3片段。在这146个氨基酸片段中，赤拟谷盗的GABA受体与果蝇以及德国小蠊Rdl亚基相应的受体分别相差12个和8个氨基酸。采用相同方法，从赤拟谷盗环二烯抗性品系的cDNA中对相应的DNA区域进行了测序。虽然发现了两个突变点，但仅发现一个DNA突变导致了氨基酸移位。突变位点在M2圆柱体的第5个氨基酸处，GCT密码子的G到T转换导致丙氨酸转变为丝氨酸。这在性质上与之前报道的抗环二烯的黑腹果蝇、埃及伊蚊（Aedes aegypti）和德国小蠊抗性品系中丙氨酸到丝氨酸的突变转换相同，表明这种氨基酸变化可能是对环二烯类杀虫剂产生神经不敏感型抗性进化的原因。
