1-4 Globins (1).pdf

PART I: PROTEIN STRUCTURE & FUNCTION CH. 3: GLOBIN PROTEINS  GLOBIN STRUCTURE/FUNCTION MYOGLOBIN VS. HEMOGLOBIN Myoglobin (muscle, storage) Structure Describe the 2º, 3º, and 4º st...

PART I: PROTEIN STRUCTURE & FUNCTION CH. 3: GLOBIN PROTEINS  GLOBIN STRUCTURE/FUNCTION MYOGLOBIN VS. HEMOGLOBIN Myoglobin (muscle, storage) Structure Describe the 2º, 3º, and 4º structures of Mb & Hb What is similar, what is different? Function Where are these molecules found? What physiologic job do they perform at that site? How do the structures of Mb & Hb relate to their common and unique functions? Hemoglobin (blood, transport)  Vinyl Group Methyl Pyrrole Ring Group Binds in cleft of Mb or Hb monomer Propionate gives blood characteristic red color! Group GLOBIN STRUCTURE/FUNCTION Heme group iron ion (Fe2+) binds O2 HEME GROUP IRON ION BINDS O2 Iron binds to 6 things! The importance of histidine proximal  NO COVALENT BONDS! How is the heme itself held in place within the protein? http://pdb101.rcsb.org/motm/1 OXYGEN CARRYING CAPACITY Arterial: Oxygen in working muscle Oxygen in lungs (15 torr) (100 torr) At your table, discuss: What does each axis represent? What are the shapes of the curves? What does this tell you about O2 binding affinity (strength)? Physiologic roles of Mb vs Hb? OXYGEN CARRYING CAPACITY TENSE RELAXED Tissues Lungs weak O2 binding strong O2 binding More O2 binding promotes transition from T to R state Allostery: binding of molecule to one site affects binding properties of other sites! COOPERATIVE O2 BINDING BY Hb Not only a tertiary structure change, but the quaternary structure changes when oxygen binds Binding at one heme enhances binding at the next! https://pdb101.rcsb.org/motm/41  MODULATION OF Hb AFFINITY FOR O2 Present in high concentration in blood! Helps lower Hb affinity for O2 Oxygen needs to let go when it gets where its going MODULATION OF Hb AFFINITY FOR O2  Crazy fact: Sickle cell protects against malaria, even SICKLE CELL DISEASE the heterozygous trait and no one knows why First disease to be connected to a specific genetic mutation Identified by Linus Pauling Homozygous HbSS (both parents) ~50% sickled RBCs Sickle-Cell Disease Heterozygous HbAS (one parent)