On the Evidence for Partial Gene Duplication from Amino Acid Sequence of Bovine Glutamate Dehydrogenase

Abstract

BOVINE glutamate dehydrogenase consists of a single polypeptide chain of 500 residues¹. Engel² has proposed that the regulatory site of the enzyme was produced by duplication of the amino acid sequence of the active centre, because when sections 114–163 and 269–318 are aligned there are twelve positions where identical amino acids occur in the two sections. Engel calculated that the probability of observing twelve identical positions in two random sequences of length fifty residues was 4.3×10⁻⁶. He argued that as there are 352 possible sequences of fifty residues with which section 114–163 may be aligned without overlapping itself the overall probability is 352×4.3×10⁻⁶ (=1.5×10⁻³). On this basis the observation quoted above is highly significant. We will show here that this probability is not significant.