SHEEP HEMOGLOBIN-I OR BETA(B)13(A10)GLY-]SER - AN EXAMPLE OF A CPG MUTATION IN VERTEBRATES - CHARACTERIZATION USING FAB MASS-SPECTROMETRY AND AMINO-ACID SEQUENCING

1. The amino acid substitution which characterizes the haemoglobin I v ariant from sheep has been ascertained using a combination of Fast Ato m Bombardment mass spectrometry and protein sequencing. 2. A Ser for G ly substitution at position 13 (10 of the A helix) was found in a poly peptide with the overall sequence of the beta(B) globin. 3. On the bas is of the nucleotide sequence of the beta (B)-globin gene, a C to T tr ansition occurring on a CpG doublet is considered to be responsible fo r the amino acid substitution. 4. This represents the first observatio n of a variant sheep Hb due to a mutation which is rather common in th e human genome. 5. Amongst ruminants, serine is normally present at po sition 13 of goat and sheep epsilon(II) and gamma chains and of bovine gamma chain which had an independent and more ancient evolutionary or igin than the beta chains.