Endo Toshinori, Fedorov Alexei, de Souza Sandro J, Gilbert Walter
The Biological Laboratories, Harvard University, 16 Divinity Avenue, Cambridge, Massachusetts 02138, USA.
Mol Biol Evol. 2002 Apr;19(4):521-252. doi: 10.1093/oxfordjournals.molbev.a004107.
Are intron positions correlated with regions of high amino acid conservation? For a set of ancient conserved proteins, with intronless prokaryotic but intron-containing eukaryotic homologs, multiple sequence alignments identified residues invariant throughout evolution. Intron positions between codons show no preferences. However, introns lying after the first base of a codon prefer conserved regions, markedly in glycines. Because glycines are in excess in conserved regions, this behavior could reflect phase-one introns entering glycine residues randomly in the ancestral sequences. Examination of intron positions within codons of evolutionarily invariable amino acids showed that roughly 50% of these introns are bordered by guanines at both 5'- and 3'-ends, 25% have a G only before the intron, and 5% have a G only after the intron, whereas about 20% are bordered by nonguanine bases.
内含子位置与高氨基酸保守区域相关吗？对于一组古老的保守蛋白质，其原核生物同源物无内含子而真核生物同源物含有内含子，多序列比对确定了在整个进化过程中不变的残基。密码子之间的内含子位置没有偏好。然而，位于密码子第一个碱基之后的内含子更倾向于保守区域，在甘氨酸中尤为明显。由于保守区域中甘氨酸过量，这种行为可能反映了第一阶段内含子在祖先序列中随机进入甘氨酸残基。对进化上不变氨基酸的密码子内内含子位置的检查表明，这些内含子中约50%在5'端和3'端都与鸟嘌呤相邻，25%仅在内含子之前有一个G，5%仅在内含子之后有一个G，而约20%与非鸟嘌呤碱基相邻。
