CHEM351, Unit 2- tertiary + quarternary structures

tertiary structure

overall three dimensional arrangement of atoms in a protein

quaternary structure

the arrangement of multiple polypeptide units

what are the two main classifications of proteins?

fibrous and globular

fibrous proteins

contain fundamental units that are simple repeats of secondary structures

what are two characteristics of fibrous proteins?

they are insoluble in water and contain several hydrophobic amino acids

what are two examples of fibrous proteins?

keratin and collagen

what is the structure of keratin

supertwisted alpha helices

what is the hierarchal organization of keratin?

alpha keratin, coiled coils, protofilament, protofibril, and intermediate filament

collagen

contain three alpha chains supertwisted around each other

tropocollagen

triad units of collagen

alpha chain

helix like structure with a repeating tripeptide unit, Gly generally followed by proline and hydroxyproline

where do H-bonds occur in a tropocollagen

intermolecularly between gly and pro

collagen fibrils

supramolecular assemblies of tropocollagens

globular protein

contains segments of a polypeptide chain folded onto itself, surface is hydrophilic, core is hydrophobic

protein domains

segment of a polypeptide that is independently stable and has two separately folded regions

protein motif

recognizable patterns involving two or more secondary structures

oligomeric proteins

proteins that have quaternary structures

protomer

oligomeric protein with individual subunits

multimer

oligomeric protein with multisubunit proteins