Use of the polymerase chain reaction for homology probing of butyrylcholinesterase from several vertebrates

Genomic blots from man, monkey, cow, sheep, pig, rabbit, dog, rat, mouse, guinea pig, and chicken DNA were hybridized with probes derived from the four exons of the human butyrylcholinesterase gene (BCHE) (Arpagaus, M., Kott, M., Vatsis, K. P., Bartels, C. F., La Du, B. N., and Lockridge, O. (1990) Biochemistry 29, 124-131). Results showed that the BCHE gene was present in a single copy in the genome of all these vertebrates. The polymerase chain reaction was used to amplify genomic DNA from these animals with oligonucleotides derived from the human BCHE coding sequence. The amplified segment contained 423 bp of BCHE sequence including the active site serine of the enzyme (amino acid 198) and a component of the anionic site, aspartate 70. Amplification was successful for monkey, pig, cow, dog, sheep, and rabbit DNA, but unsuccessful for rat, guinea pig, mouse, and chicken DNA. Amplified segments were cloned in M13 and sequenced. The mouse sequence was obtained by sequencing a genomic clone. The highest identity of the human amino acid sequence was found with monkey (100%) and the lowest with mouse (91.5%). The sequence around the active site serine 198, Phe-Gly-Glu-Ser-Ala-Gly-Ala, was conserved in all eight animals as was the anionic site component, aspartate 70. A phylogenetic tree of mammalian butyrylcholinesterases was constructed using the partial BCHE sequences.