There are almost 500 naturally occurring variants of hemoglobin. Most are the result of a single amino acid substitution in a globin polypeptide chain. Some variants produce clinical illness, though not all variants have deleterious effects. A brief sample follows. HbS (sickle-cell Hb): substitutes a Val for a Glu on the surface Hb Cowtown: eliminates an ion pair involved in T-state stabilization Hb Memphis: substitutes one uncharged polar residue for another of similar size on the surface Hb Bibba: substitutes a Pro for a Leu involved in an _helix Hb Milwaukee: substitutes a Glu for a Val Hb Providence: substitutes an Asn for a Lys that normally projects into the central cavity of the tetramer Hb Philly: substitutes a Phe for a Tyr, disrupting hydrogen bonding at the alßl1 interface Explain your choices for each of the following: (a) The Hb variant least likely to cause pathological symptoms. (b) The variant(s) most likely to show pl values different from that of HbA. (c) The variant(s) most likely to show a decrease in BPG binding and an increase in the overall affinity of the hemoglobin for oxygen.

There are almost 500 naturally occurring variants of hemoglobin. Most are the result of a single amino acid substitution in a globin polypeptide chain. Some variants produce clinical illness, though not all variants have deleterious effects. A brief sample follows. HbS (sickle-cell Hb): substitutes a Val for a Glu on the surface Hb Cowtown: eliminates an ion pair involved in T-state stabilization Hb Memphis: substitutes one uncharged polar residue for another of similar size on the surface Hb Bibba: substitutes a Pro for a Leu involved in an _helix Hb Milwaukee: substitutes a Glu for a Val Hb Providence: substitutes an Asn for a Lys that normally projects into the central cavity of the tetramer Hb Philly: substitutes a Phe for a Tyr, disrupting hydrogen bonding at the alßl1 interface Explain your choices for each of the following: (a) The Hb variant least likely to cause pathological symptoms. (b) The variant(s) most likely to show pl values different from that of HbA. (c) The variant(s) most likely to show a decrease in BPG binding and an increase in the overall affinity of the hemoglobin for oxygen.

Human Physiology: From Cells to Systems (MindTap Course List)

9th Edition

ISBN:9781285866932

Author:Lauralee Sherwood

Publisher:Lauralee Sherwood

Chapter11: The Blood

Section: Chapter Questions

Problem 3SQE

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