-Glu91 of strand 7 and Arg122 of strand 8. This bridge acts as a lid to the barrel and is located opposite the binding sight.
-Arg100 of strand 7 and Asp109 of loop 7-8.
-Asp108 and Lys111.
- Several polar residues are in the binding pocket are available for hydrogen bonding on biotin's ureidic ring. N-13 is bound to the oxygen on
Asn118. O-12 has strong interactions with OG of
Ser16 and OH of Tyr33. N-11 is bonded to oxygen of
Thr35.
-
The aromatic residues of
Phe79
and
Trp97
surround biotin's tetrahydrothiophenic ring and stablize.
-
-Biotin's terminal carboxylate group is Hydrogen bonded to
Ala39, Thr40,
Ser73, Ser 75.
-
The avidin-biotin complex is extremely tight and stable, the complex is stable in 9 M Urea. Tryptophan residues 70, 97 and 110 are thought to be involved in recognition of biotin.
-
In each chain of avidin, when biotin is bound
it is in close contact with Trp 70 and Trp 97.