Protein Structure and Function

Protein Structure and Function

• Proteins are the building blocks of life, composed of one or more chains of amino acids.
• Proteins perform diverse functions, including: catalyzing reactions (enzymes), providing support (structural proteins), carrying molecules (transport proteins), storing molecules, signaling, and having a special purpose.
• Proteins have 4 levels of structure:
  • Primary: The linear sequence of amino acids.
  • Secondary: Interactions between close amino acids forming alpha helices and beta sheets.
  • Tertiary: Interactions between secondary structures and distant amino acids creating a 3D shape.
  • Quaternary: Interactions between multiple polypeptide chains to create a larger complex structure.
• Protein structure is vital for function. Correct folding is necessary for proper activity.
• Protein folding is influenced by hydrophobic core collapse, energy-entropy, and chaperone proteins.
• Misfolded proteins can result in various diseases.

Central Dogma

• Genetic information flows from DNA to RNA to protein.
• DNA is transcribed into RNA, which is then translated into protein.
• RNA carries the genetic information from the DNA in the nucleus to the ribosomes in the cytoplasm, where proteins are synthesized.
• Many copies of RNA can be made from one gene, enabling the rapid synthesis of a protein.

Translation

• Translation is the conversion of genetic information in RNA to protein.
• The genetic code specifies the correspondence between nucleotide triplets (codons) in DNA or RNA and amino acids in proteins.
• A codon is a group of three consecutive nucleotides in RNA, and each codon specifies a single amino acid.
• Reading frames describe how a string of nucleotides is translated into a protein.

Amino Acids

• Amino acids are the building blocks of proteins.
• Each amino acid has a central carbon atom (alpha carbon) bonded to a carboxyl group, an amino group, and a hydrogen atom.
• The side chain (R group) distinguishes each amino acid and gives it its unique characteristic.
• The twenty standard amino acids are linked by peptide bonds to form proteins.

Protein Folding

• Protein folding is crucial to protein function. Improper folding leads to dysfunction or disease.
• The native protein shape (3-D structure) is determined by the sequence of its amino acids.
• The process is described by Anfinsen's dogma.

Protein Parameters

• Protein parameters include:
  • Number of amino acid residues
  • Number of subunits
  • Protein molecular mass (Da or kDa)
  • Isoelectric point (pI) -These parameters can be predicted using software.

Allostery

• Allosteric effects describe how the binding of a ligand at one site in an oligomeric protein affects the binding of a ligand at another site.
• Allostery involves a change in protein conformation.
• Allosteric effects are important in many biological processes, including enzyme regulation and oxygen binding to hemoglobin.

Other Relevant Information

• The 20 standard amino acids are further classified according to different properties of their side chains (R-groups).
• Important techniques for determining protein structure include X-ray crystallography and NMR.
• Various methods of reducing disulfide bonds involved in the creation of a protein also exist.
• Additional important information about protein interactions, and special protein classes was also covered, like antibodies.