8/22 - Chapter 4: Globular & Fibrous Proteins

Globular protein

spherical shaped and somewhat water soluble

Globular protein core

nonpolar, van der waals forces

Globular protein surface

Charged, polar, salt bridges

Globular protein functions

storage of ions and molecules, transport of ions and molecules, defense against pathogens, muscle contraction, biological catalysis

Fibrous proteins

forms long protein filaments, shaped like rods that are typically inert and water-soluble

Actin fold

ATP binds to the middle of the cleft of the actin fold, promoting a change closing the cleft; ATP is cleaved to ADP

Nucleotide binding fold

binding site for NAD+

Hemoglobin

found only in red blood cells, transporting H+ and CO2 from tissues to the lungs and O2 from lungs to tissues

Allosteric effects regulating hemoglobin

pO2, pH/pCO2, 2,3-bisphosphyoglycerate

CO poisoning

CO has a similar size and shape to O2 and can fit to the same binding site, competing with oxygen and blocking the function of myoglobin, hemoglobin, and mitochondrial cytochromes

Fetal hemoglobin (HbF)

major hemoglobin found in newborns with a higher affinity for O2 than HbA; transfers O2 from maternal to fetal circulation across placenta

HbA2

appears shortly before birth

HbA1C

high in patients with diabetes mellitus; undergoes glycosylation, which depends on plasma glucose levels

Sulf-Hb

forms because of high sulfur levels, sulfhemoglobinemia; irreversible

Carboxy-Hb

CO2 replaces O2 and binds 200x faster, carboxyhemoglobin; common in smokers

Met-Hb

contains Fe3+ that cannot deliver O2, methemoglobemia; acquired and congenital, reversible with methylene blue infusion

Hemoglobinopathies

structural defects in hemoglobin, diminished production of one of the two subunits, or abnormal associations of otherwise abnormal subunits

What are major hemoglobinopathies?

Sickle cell disease, thallasemia, hemoglobin C disease, Hemoglobin SC disease