the amino-acid residues substituted in the alpha-chains are not involved in any contacts , whereas in the beta-chains , one exchange involves a heme contact , three alpha 1/beta 1- and one alpha 1/beta 2-contacts , the latter [ beta 43 ( cd2 ) -glu -- -- thr ] brings for the first time threonine in this position of the beta-chains .
C0002520
amino-acid
C0061472
glu