The amino acid sequence of apovitellenin I from hen egg yolk has been determined using both automatic and manual procedures; it comprises 82 residues. Hen apovitellenin shows considerable homology with emu apovitellenin I which contains 84 residues. Besides two deletions in the sequence, the hen protein differs in 28 positions from the emu protein; 26 of these positions may have arisen from single base changes. The changes are largely conservative ones, which suggest that the structure and function have been preserved despite extensive mutation.

The amino acid sequence of apovitellenin I from emu (Dromaius novae-hollandiae) egg yolk has been determined. Difficulties were encountered during sequencing, due to a labile Tyr-Val bond, which was hydrolysed readily by trypsin, chymotrypsin and pepsin. By use of a sequenator, this bond was easily characterized. The protein contains 84 residues and is devoid of half-cystine and histidine. Hydrophobic residues occur in clusters; two very hydrophobic sequences of 12 and 13 residues are present. A very hydrophilic sequence of seven residues contains nearly one-third of all side-chain charges in the molecule; the remainder of the polar residues are scattered throughout the sequence. In a number of instances, residues with opposite charges occur in adjacent positions.