Broomfield P L, Hargreaves J A
Department of Agricultural Sciences, University of Bristol, UK.
Curr Genet. 1992 Aug;22(2):117-21. doi: 10.1007/BF00351470.
The sequence of an allele encoding the iron-sulphur protein (Ip) subunit of succinate dehydrogenase (Sdh) was determined following PCR amplification of genomic DNA from a carboxin (Cbx)-sensitive Ustilago maydis strain. Comparison of this sequence with that of the Ip allele from a Cbx-resistant strain (IPr) revealed a two-base difference between the sequences. This mutation led to the substitution of a leucine residue for a histidine residue within the third cysteine-rich cluster of the deduced amino-acid sequence of the Ipr allele. This cluster, which is associated with the S3 iron-redox centre, is involved in the transport of electrons from succinate to ubiquinone (Q). Confirmation that this nucleotide change led to enhanced resistance to Cbx was obtained following mutagenesis of the sensitive Ip allele to the resistant form and expression of the mutated allele in U. maydis.
从对羧苄青霉素（Cbx）敏感的玉米黑粉菌菌株中提取基因组DNA，经PCR扩增后，测定了琥珀酸脱氢酶（Sdh）的铁硫蛋白（Ip）亚基编码等位基因的序列。将该序列与来自对Cbx有抗性的菌株（IPr）的Ip等位基因序列进行比较，发现两者之间存在两个碱基差异。该突变导致在IPr等位基因推导的氨基酸序列的第三个富含半胱氨酸的簇中，一个组氨酸残基被一个亮氨酸残基取代。这个与S3铁氧化还原中心相关的簇，参与了电子从琥珀酸到泛醌（Q）的传递。通过将敏感的Ip等位基因突变成为抗性形式，并在玉米黑粉菌中表达突变后的等位基因，证实了这种核苷酸变化导致对Cbx的抗性增强。
