JMS/sandboxBarkai

It comes down to . Without these amino acids, myoglobin in both whale and elephants has a charge of +1. With them, whale myoglobin has a net charge of +4 and elephants of +2. Importantly, all eight of these divergent amino acids are .

Calculate along the chain, in the N to C-terminal direction how just several amino acid switches bring the positive net charge of whale myoglobin up to +4 and elephants to +2: (summing up the total charge of the protein) (glu in elephents versus gln in whales), (lys vs. his), (thr vs. asp), (thr vs. lys ), (gln vs. lys ), (gln vs. his), (lys vs. asn), (asn vs. lys ).

• note about illustration: Asp and Glu have a charge of -1, Arg and Lys have a charge of +1, His in the positions shown here - 12 and 116 (Table S2^[1]) - have a charge of about +0.5.