lecturer 5 Flashcards
_______ ______typically occurs by enzymes sensing too much product for their reaction building up via a special regulatory site on the enzyme
Feedback inhibition
Phosphorylation of some substrates by ____ _____can serve to inactivate protein functions
protein kinases
GTP is bound to the protein and converted to _______ as it acts on another protein
GDP + Pi
When a protein binds a ligand or another protein and this induces a conformational change that opens another binding site in the molecule this is known as
allosterism
The ____ _____ ____ or concentration of any individual species of protein in the cell will be a unique function of the factors controlling both its _______ &______ .
steady state level, synthesis (production) and degradation (destruction)
The half-life of a protein is
is half the average number of minutes (or hours) the protein spends in the cell
Ribosomes free in the cytosol and associated with _____ ______
the ER membranes
Misfolded proteins in the cell can be degraded by what structures
Proteasomes
The posttranslational modification that targets proteins to the proteasome is
Ubquitylation
Protein degradation occurs by two mechanisms
Proteasomes, Lysosomes
degrade cellular proteins that are damaged or that have been specifically targeted for degradation by modification with _____
ubiquitin
Lysosomes (defining factor)
are a membrane bound cellular compartment containing proteases degradation of proteins found in membranes or soluble proteins imported into the cell.
Regulated ubiquitin
modification leads to
degradation
what is a type of sequestration that can hold can some transcription factors in the cytosol until signals cause modifications that allow their entry into the nucleus where they can function
localization
Proteins are typically not active until they have assembled into their
quaternary structures
alpha and beta subunits are _________ alone until they assemble into
non-functional
Many enzymatic reactions or pathways are
self-regulated by feedback inhibition mediated
by
the end products
Transcabamoylase catalyzes an early step in synthesis of pyrimidine nucleotides. CTP a _____ _____ of this pathway the ______ enzyme
downstream product, inhibits
sequestering proteins____ and prevent assembly
bind
what is a change due to binding of a ligand that promotes the binding of a second ligand
allosteric
what are 4 key mechanisms that control protein activities
Modification by attachment of ubiquitin to lysine residues
Modification by protein phosphorylation/dephosphorylation
Nucleotide binding and hydrolysis
Modification by lipid anchor addition to C terminal Cys
By modifying proteins, cells create at least __ potential states of activity for _________________
two, any modified protein
modifying proteins can _______ functionality without having to ________________
increases, synthesize more proteins.
Combinatorial control
groups of regulatory proteins work together to determine teh expression of a single gene
eucaryotes can make more complicated tissues and organisms because
Combinations of regulation on synthesis points and post-translational modifications
Protein ________ and _____ carry out the reversible modification of many substrate proteins
kinases, phosphatases,
binding of the nucleotides ATP/ADP and GTP/GDP….
produces conformation changes controlling protein activities.
Conformation changes due to ______ binding and ______ in Elongation Factor Tu during translation
nucleotide, hydrolysis
what anchors or localizes proteins to different membranes
Lipid added to proteins
what are examples of lipid additiom
GPI) of Prion proteins; prenylation of Ras and Rho proteins affecting growth
Modifications that are part of the “histone code”include __________&________
occur as covalent modifications of
_____ _____ ____
methylation and acetylation, basic amino acids
DNA + histone =
nucleaosome
