protein folding Flashcards
Difference between protein deactivation and denaturation: Denatured protein is () but inactive is not necessarily () .
Denaturation = complete loss of () () () or () ,of protein all the way to () structure.
Inactive= form of regulation controlling () of protein involving () yet () modification.
Difference between protein deactivation and denaturation: Denatured protein is inactive but inactive is not necessarily denaturated .
Denaturation = complete loss of secondary and tertiary or unfolding of protein all the way to primary structure.
Inactive= form of regulation controlling function of protein involving reversible yet covalent modification.
Proteins can undergo phosphorylation and de-phosphorylation, leading to active or inactive. Example: () and () ; both are required to maintain glycogen () . Both exist in phosphorylated and dephosphorylated forms.
In glycogen () : which is responsible of glycogen () and release of() , inactive in () form. On the other hand: glycogen () inactive in () form and it catalyzes the conversion of glucose-6-p to glycogen.
Other examples include () ()
from () pathway and active as ().
Covalent modification is not always () : for example () : typical example: () which are () () enzymes that are activated when needed (following ingestion of meal) by () () (covalent modification) of a () () generating an active () like () into () or () into ().
Another example are () reffered to as () () () (intracellular proteases) are also covalently and irreversibly modified.
Other forms of covalent modification is () () such as that occuring in () () () protein, a family of () that plays a central role in cancer development. () is another form, involving () (() acid) of () residue plays a role in () () and in signal transduction recruiting () protein to interact with receptor.
Another form of activation/inactivation that is very important being rapid and reversible is () () or () where small molecules occupy a site other than the active site modulating it positively or negatively (activators or inhibitory). This is one important regulator of pathways when effectors/modulators act on () () step enzyme.
The interaction of allosteric modulators with proteins is ()
Finally one of unusual form of regulation is () () : () of proteins activates the protein typical example is () () () () renders the enzyme active, stimulating () ()(). Other cases the () activates the enzymes like () : () () () function is () () is active as () and less active as a ().
Proteins can undergo phosphorylation and de-phosphorylation, leading to active or inactive. Example: glycogen phosphorylase and glycogen synthase ; both are required to maintain glycogen homeostasis. Both exist in phosphorylated and dephosphorylated forms.
In glycogen phosphorylase : which is responsible of glycogen hydrolysis and release of glucose-6-p , inactive in dephosphorylated form. On the other hand: glycogen synthase inactive in phosphorylated form and it catalyzes the conversion of glucose-6-p to glycogen.
Other examples include HMGoA reductase from cholesterol pathway and active as phosphorylated.
Covalent modification is not always irreversible : for example proteolysis : typical example: zymoges which are inactivated digestive enzymes that are activated when needed (following ingestion of meal) by proteolytic cleavage (covalent modification) of a small peptide generating an active protein like pepsinogen into pepsin or trypsinogen into trypsin.
Another example are caspases reffered to as cysteine aspartate proteases (intracellular proteases) are also covalently and irreversibly modified.
Other forms of covalent modification is protein prenylation such as that occuring in RAT sarcoma RAS protein, a family of GTPases that plays a central role in cancer development. Acylation is another form, involving myritoylation (C14 acid) of glycine residue plays a role in membrane targeting and in signal transduction recruiting G protein to interact with receptor.
Another form of activation/inactivation that is very important being rapid and reversible is allosteric effectors or modulators where small molecules occupy a site other than the active site modulating it positively or negatively (activators or inhibitory). This is one important regulator of pathways when effectors/modulators act on rate determining step enzyme.
The interaction of allosteric modulators with proteins is non covalent
Finally one of unusual form of regulation is conformational changes: polymerization of proteins activates the protein typical example is acetyl coA polymerization renders the enzyme active, stimulating fatty acid synthesis. Other cases the depolymerization activates the enzymes like PRA: phosphoribosyl amino transfera function is purine syntheies is active as monomer and less active as polymer.
Denaturation is irreversible most of the time.
Some have ability to renature depending on the nature of the () () . Adding vinegar to milk denature proteins and allow them to precipitate.
What causes denaturation: mechanical beating / mixing, improper handing of protein, adding of oxidizing or reducing agents.
Heating them in general changes the () + () of proteins. Some of them may withstand the increase like () () enzyme used in () () () tolerate () cycles of heating to () degrees then cooling.
Heating in general increases the () () stimulating the bombardment of protein molecules which favors disruption of () and() () (() and () structures)
Denaturation is irreversible most of the time.
Some have ability to renature depending on the nature of the denaturing agent . Adding vinegar to milk denature proteins and allow them to precipitate.
What causes denaturation: mechanical beating / mixing, improper handing of protein, adding of oxidizing or reducing agents.
Heating them in general changes the conformation and properties of proteins. Some of them may withstand the increase like Taq polymerase enzyme used in pcr amplifying gene tolerate >20 cycles of heating to 70 degrees then cooling.
Heating in general increases the kinetic energy stimulating the bombardment of protein molecules which favors disruption of H-bonding and ionic interactions (sec and ter structures)
Strong acids or bases will disrupt electrostatic interactions affecting tertiary, quaternary structures. The acid will () the () () and the base will () the () () In both cases either agents will disrupt positive-negative ionic interactions
Strong acids or bases will disrupt electrostatic interactions affecting tertiary, quaternary structures. The acid will protonate the conjugate base and the base will deprotonate the conjugate acid. In both cases either agents will disrupt positive-negative ionic interactions
Alcohol have both hydrophobic and hydrophilic groups that allows it to interfere with () and ()
Alcohol have both hydrophobic and hydrophilic groups that allows it to interfere with H-bonding and hydrophobic hydrophobic interaction
