Hb savannah with val 4 mutaons that stabilize

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Unformatted text preview: n cells (lysis), low [Hb], “sickle cell anemia” Sickled erythrocyte Berg, Tymoczko, & Stryer, Biochemistry, 6th ed. Fig. 7-23 Other mutant hemoglobins 2. muta:ons that lead to loss of heme, muta:ons in heme binding pocket Hb Hammersmith [βF42S] •  •  •  •  Phe  ­ ­> Ser muta.on HbA: Phe blocks access of H2O to heme pocket. smaller, polar Ser permits H2O to enter. H2O dislodges heme from pocket  ­ ­ ­> nonfunc.onal Hb. βF42 3. muta:ons that disrupt ter:ary structure of a subunit HbA with Gly Hb Savannah [βG24V] Gly --> Val mutation HbA: two helices (B helix, red and E helix, green in figure below) so close together that there’s only room for Gly at B6 between them. Hb Savannah: Val sidechain pushes B and E helices apart, disrupting tertiary structure of β chain, so Hb structure is unstable. Hb Savannah with Val 4. muta:ons that stabilize methemoglobin (Fe3+) •All known methemoglobins result from muta.ons that provide a nega.vely charged oxygen atom as...
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