Evolution of Intradiol Dioxygenase Genes in Bacteria

这项研究计划旨在探索相邻DNA序列如何影响基因的属性和基因内区域的稳定性。细菌的双加氧酶基因是研究的对象，它们有着共同的祖先，并在进化分化过程中经历了多次重排。重排可能会导致独立转录基因的物理分离，但不同的加氧酶基因的染色体位置在不同的膜上簇中是保守的。通过检查加氧酶基因从一个簇到另一个簇的定向转座的生理和遗传后果，将探索有利于基因簇的选择性力量。转座可以导致遗传不稳定，而不稳定的一个可能来源是序列定向突变，这一过程可能导致DNA序列重复区域之间的缺失。通过比较在正常位置或转座到不同簇后发生自发突变的基因的DNA序列，将探索发生序列定向突变的程度。导致序列定向突变的过程也可能有助于基因修复，这种可能性将通过分析容易逆转的突变的DNA序列来探索。酶激活氧是一个基本的生物学过程，对加氧酶的遗传分析将增加我们对生物化学步骤的了解，这些步骤直接将分子氧同化到有机底物中。我们计划分离具有功能但底物特异性或催化效率改变的突变加氧酶。对这些蛋白质的分析可能会为加氧酶及其底物之间的相互作用提供新的见解。

The research program is designed to explore how the properties of genes and the stability of regions within genes are influenced by neighboring DNA sequences. Bacterial intradiol dioxygenase genes, the subjects of the investigation, share common ancestry and have undergone numerous rearrangements during their evolutionary divergence. Rearrangements might be expected to lead to the physical separation of independently transcribed genes, but the chromosomal position of divergent oxygenase genes has been conserved within different supraoperonic clusters. Selective forces favoring the clustering of genes will be explored by examining the physiological and genetic consequences of directed transposition of oxygenase genes from one cluster to another. Transposition can lead to genetic instability, and a possible source of instability is sequence-directed mutation, a process that can lead to deletions between regions of DNA sequence repetition. The extent to which sequence-directed mutations occur will be explored by comparison of the DNA sequences of genes that have undergone spontaneous mutation either in their normal location or after transposition to a different cluster. Processes that lead to sequence-directed mutation also might contribute to genetic repair, and this possibility will be explored by analysis of DNA sequence of mutations that revert readily. Enzymatic activation of oxygen is a fundamental biological process, and the genetic analysis of oxygenases will increase our understanding of biochemical steps that direct the assimilation of molecular oxygen into organic substrates. We plan to isolate mutant oxygenases that are functional but altered in substrate specificity or in catalytic efficiency,. Analysis of these proteins is likely to provide novel insight into interactions between oxygenases and their substrates.