黄牛（Bos taurus）基因组P450基因家族的分析

利用黄牛基因组cDNA和氨基酸数据库对P450基因进行搜索和分析，结果显示：在黄牛基因组中发现64个P450基因，分别属于18个P450家族和38个亚家族。以氨基酸序列相似度大于60％为标准对黄牛P450基因进行分组，32个为孤儿基因，其余32个可归入9个组，其中7个组适合于正选择和基因转换分析。结果表明：有3个组显著受到正选择压力作用，其中的2个组有正选择概率大于95％的氨基酸位点，分别位于底物识别位点SRS1和SRS2；有5个组显示显著的基因转换事件；既显著受到正选择压力作用，又参与基因转换的基因共4个。可见，发生基因转换的基因与受到显著正选择的基因有一定的相关性。此外，鉴定出20个不同的基序，其中有6条基序在90％以上的基因中出现。

A Genome-wide Analysis of P450 Gene Family in Cow(Bos taurus)

A genome-wide analysis of P450 genes were performed in cow genome based on their eDNA and amino acid data. Sixty-four P450 genes, assigned into 18 gene families and 38 subfamilies, were identified. All P450 genes were partitioned into 9 groups and 32 orphan genes by a criterion that the genes belong to a group when their amino acid identity were more than 60 %. Positive selection and gene conversion were analyzed in other 7 groups. The results showed that positive selections were detected in 3 groups. The positively selected sites, locating in SRS （ substrate recognition sites） 1 and SRS 2, were detected in 2 groups with a more than 95 % probability. And gene conversions were detected in 5 groups. Interestingly, both positive selection and gene conversion events were identified obviously in 4 genes. The certain correlation was revealed between positive selection and gene conversion. Moreover, twenty motifs were identified, thereinto, 6 motifs existed in over 90 % of P450 genes.