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 alß1 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 alß1 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.
Biochemistry
9th Edition
ISBN:9781319114671
Author:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.
Publisher:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.
Chapter1: Biochemistry: An Evolving Science
Section: Chapter Questions
Problem 1P
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Actually my head was confused in case (c). Is the answer just Hb Providence ? or Hb Cowtown and Hb Providence both?
Transcribed Image Text: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 alß1 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 pI 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.
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