Question

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 of hemoglobin variants is given. 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 $\alpha$ 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 $\alpha_1\beta_1$ interface Select the hemoglobin variant(s) that are described by each statement. (a) The variant least likely to cause pathological symptoms (b) The variant(s) likely to show pI values different from that of HbA on an isoelectric focusing gel

Name: 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 t 27626
Uploaded: 2020-12-24T07:10:59-08:00
Duration: 7 min 2 s
Channel: Prashant Bana
Description: 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 t 27626

          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 of hemoglobin variants is given.
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 $\alpha$ 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 $\alpha_1\beta_1$ interface

Select the hemoglobin variant(s) that are described by each statement.

(a) The variant least likely to cause pathological symptoms

(b) The variant(s) likely to show pI values different from that of HbA on an isoelectric focusing gel

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 t 27626

Added by Kathy J.

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