Polyacrylamide gel electrophoresis in urea and Triton X-100 of a hemolysate from human fetal red blood cells produces four major protein bands: α, β and 2 γ globin chains. We have G A verified that the latter two are the Gγ and Aγ globin chains which have respectively glycine or alanine at position 136. After incorporation of either [3H] alanine or [3H] glycine into newly synthesized globin each γ chain was isolated by preparative electrophoresis. The chains were cleaved with cyanogen bromide at methionines 55 and 133, then subjected to automated sequencing, and the residues from each sequencer turn counted. Glycine incorporation was detected for the third turn (position 136) of the Gγ chain and alanine for the Aγ. Substantial metabolic conversion of [3H] [H] glycine to serine and proline was also noted.
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