Question

There are almost 500 naturally occurring variants of hemoglobin. Most are the result of a single amino ad substitution in a globin polypeptide chain. Some variants produce clinical illness, though not all variants have deleterious effects Identify the variant or variants that can be described by each of the three statements at the right by placing the letter corresponding to the statement in the blue oútlined rectangle next to the variant. StatementB may describe more than one variant, and a variant may be described by more than one statement. Some variants will not match any description B HbS (sickle-cell Hb): substitutes a Val for a Glu on the B Hb Cowtown: eliminates an ion pair involved in T-state A Hb Memphis: substitutes one uncharged polar residue for Variant Description surface A. The Hb variant least likely to cause pathological symptoms stabilization B. The variants most likely to show pl values different from that of HbA on an isoelectric focusing gel another of similar size on the surface Hb Bibba: substitutes a Pro for a Leu involved in an a C. The variant most likely to show a helix Hb Milwaukee: substitutes a Glu for a Val Hb Providence: substitutes an Asn for a Lys that normally decrease in BPG binding and arn increase in overall affinity for oxygen c projects into the central cavity of the tetramer B Hb Philly: substitutes a Phe for a Tyr, disrupting hydrogen bonding at the ap interface Incorrect. At least one of the variants is not described correctly. Substitution of a Pro for a Leu involved in a helix will not have any effect on the pl but will most likely cause a major structural alteration in the molecule

Answer 1

B and C- Hb Province: substitutes an Asn for a Lys that normally projects into the central cavity of the tetramer- The variant(s) most likely to show pI values different from that of HbA on an isoelectric focusing gel and C also.

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