MODULE C7: Post-translational Modifications and 3D Structure of Proteins

Flashcards for reviewing key concepts on post-translational modifications and protein structure.

Post-translational modifications

Changes to proteins that occur after synthesis, crucial for achieving active conformation.

Protein synthesis stages

Five stages including activation, initiation, elongation, termination, and post-translational processing.

Amino acids

Organic compounds that serve as the building blocks of proteins, containing an amino group, carboxyl group, and R group.

tRNA

Transfer RNA, responsible for carrying amino acids to the ribosome during protein synthesis.

Peptide bond

A covalent bond formed between two amino acids through a condensation reaction.

Hydrophobic R groups

Amino acid side chains that are nonpolar and tend to avoid water.

Cysteine

A polar, uncharged amino acid that can form disulfide bonds, contributing to protein stability.

Dipeptide

A molecule formed from two amino acids linked by a peptide bond.

Acetylation

The addition of an acetyl group to the N-terminal residue of a protein.

Secondary structure

Local spatial arrangement of a polypeptide chain; common forms include alpha helices and beta sheets.

Alpha helix

A common secondary structure in proteins stabilized by hydrogen bonds between nearby residues.

Beta sheet

A secondary structure in proteins stabilized by hydrogen bonds between adjacent segments.

Side chains

Variable groups attached to amino acids that determine their properties and roles.

Folding

The process of a protein adopting its functional three-dimensional structure.

Tertiary structure

The overall three-dimensional shape of a polypeptide chain.

Quaternary structure

The arrangement of multiple polypeptide chains into a functional protein complex.

Hydrophobic effect

The tendency of nonpolar substances to aggregate in aqueous solutions to minimize their exposure to water.

Prosthetic groups

Non-polypeptide components tightly and permanently attached to proteins, crucial for their function.

Coenzyme

An organic molecule that assists enzymes in catalyzing reactions.

Motifs

Simple combinations of secondary structure elements that have specific functions.

Transient modifications

Reversible changes to proteins that often play a role in regulation and signaling.

Disulfide bonds

Covalent bonds formed between the sulfhydryl groups of cysteine residues, stabilizing protein structure.

Residue

An amino acid unit within a peptide or protein after it has been incorporated into the chain.

Pauling's rules

Rules that govern the structural properties of proteins, including the formation of secondary structures.

Ramachandran plot

A graphical representation of allowed regions of torsion angles for a polypeptide chain.

Aromatic amino acids

Amino acids with aromatic side chains, such as phenylalanine, tyrosine, and tryptophan.

Nonpolar amino acids

Amino acids with hydrophobic side chains, such as glycine, alanine, and valine.

Basic amino acids

Amino acids with positively charged side chains at physiological pH, such as lysine and arginine.

Acidic amino acids

Amino acids with negatively charged side chains at physiological pH, such as aspartate and glutamate.

Peptide synthesis

The chemical process by which amino acids are sequentially linked to form peptides.

Glycine

The smallest amino acid, which has a nonpolar side chain and can fit in tight spaces within proteins.

Alanine

A nonpolar amino acid that is often utilized in the synthesis of proteins.

Leucine

A nonpolar, branched-chain amino acid that plays a key role in protein structure.

Isoleucine

An essential amino acid similar to leucine, important for protein synthesis.

Valine

A branched-chain amino acid associated with muscle metabolism and tissue repair.

Amino acid segregation

The arrangement of amino acids in proteins that affects their function and interaction.

Peptide linking

The formation of peptide bonds through a dehydration reaction between amino acids.

Protein conformation

The specific three-dimensional arrangement of a protein's structure essential for its functionality.

Binding domains

Regions of a protein that are responsible for binding to other molecules.

Peptide sequences

The order of amino acids in a protein that ultimately determines its function.

Protein stability

The ability of a protein to maintain its structure under various conditions.

Multimeric proteins

Proteins composed of more than one polypeptide chain.

Signal sequences

Stretch of amino acids in a protein that direct it to specific locations within the cell.

Hydrogen bonds in proteins

Weak bonds that help stabilize the secondary and tertiary structures of proteins.

Structural domains

Distinct functional and/or structural units within a protein that can evolve independently.

Enzyme activation

The process of changing an enzyme to its active form, often through post-translational modifications.

Electrostatic interactions

Forces between charged side chains in proteins that contribute to their stability and shape.

Conformational entropy

The measure of the number of possible shapes a protein can adopt, important in folding.