retinoblastoma protein

Examples of retinoblastoma protein in the following topics:

• Regulator Molecules of the Cell Cycle

  • Phosphorylation activates the protein by changing its shape.
  • The best understood negative regulatory molecules are retinoblastoma protein (Rb), p53, and p21.
  • Retinoblastoma proteins are a group of tumor-suppressor proteins common in many cells.
  • The concentrations of cyclin proteins change throughout the cell cycle.
  • Cyclin-dependent kinases (Cdks) are protein kinases that, when fully activated, can phosphorylate and activate other proteins that advance the cell cycle past a checkpoint.

• Regulating Protein Activity and Longevity

  • The addition of a phosphate group to a protein can result in either activation or deactivation; it is protein dependent.
  • The addition of methyl groups to a protein can result in protein-protein interactions that allows for transcriptional regulation, response to stress, protein repair, nuclear transport, and even differentiation processes.
  • Methylation in the proteins negates the negative charge on it and increases the hydrophobicity of the protein.
  • The addition of an ubiquitin group to a protein marks that protein for degradation.
  • These proteins are moved to the proteasome, an organelle that functions to remove proteins to be degraded .

• Denaturation and Protein Folding

  • This shape determines the protein's function, from digesting protein in the stomach to carrying oxygen in the blood.
  • If the protein is subject to changes in temperature, pH, or exposure to chemicals, the internal interactions between the protein's amino acids can be altered, which in turn may alter the shape of the protein.
  • Although the amino acid sequence (also known as the protein's primary structure) does not change, the protein's shape may change so much that it becomes dysfunctional, in which case the protein is considered denatured.
  • Chaperone proteins (or chaperonins) are helper proteins that provide favorable conditions for protein folding to take place.
  • (Top) The protein albumin in raw and cooked egg white.

• Protein Folding, Modification, and Targeting

  • The native conformation of a protein is a stable three-dimensional structure that strongly determines a protein's biological function.
  • When a protein loses its biological function as a result of a loss of three-dimensional structure, we say that the protein has undergone denaturation.
  • The denatured state of the protein does not equate with the unfolding of the protein and randomization of conformation.
  • These sequences at the amino end or the carboxyl end of the protein can be thought of as the protein's "train ticket" to its ultimate destination.
  • This protein serves as a channel for chloride ions.

• Facilitated transport

  • In both cases, they are transmembrane proteins.
  • Another type of protein embedded in the plasma membrane is a carrier protein.
  • Carrier proteins are typically specific for a single substance.
  • Each carrier protein is specific to one substance, and there are a finite number of these proteins in any membrane.
  • Channel proteins transport much more quickly than do carrier proteins.

• The Complement System

  • Cells of the liver and macrophages synthesize complement proteins continuously.
  • Binding of complement proteins occurs in a specific and highly-regulated sequence, with each successive protein being activated by cleavage and/or structural changes induced upon binding of the preceding protein(s).
  • After the first few complement proteins bind, a cascade of sequential binding events follows in which the pathogen rapidly becomes coated in complement proteins.
  • Complement proteins perform several functions.
  • Pathogens lacking these regulatory proteins are lysed.

• Basic Techniques in Protein Analysis

  • The basic techniques used to analyze proteins are mass spectrometry, x-ray crystallography, NMR, and protein microarrays.
  • Protein microarrays have also been used to study interactions between proteins.
  • One protein of interest is genetically fused to the BD and another protein is fused to the AD.
  • The western blot, or protein immunoblot, is a technique that combines protein electrophoresis and antibodies to detect proteins in a sample.
  • A protein called the bait is attached to the BD, and a protein called the prey is attached to the AD.

• Types and Functions of Proteins

  • Proteins perform essential functions throughout the systems of the human body.
  • Sometimes non-polypeptide groups are also required in the final protein.
  • Because form determines function, any slight change to a protein's shape may cause the protein to become dysfunctional.
  • Some proteins function as chemical-signaling molecules called hormones.
  • From the protein data base.

• The Central Dogma: DNA Encodes RNA; RNA Encodes Protein

• Protein Structure

  • The shape of a protein is critical to its function because it determines whether the protein can interact with other molecules.
  • Protein structures are very complex, and researchers have only very recently been able to easily and quickly determine the structure of complete proteins down to the atomic level.
  • To determine how the protein gets its final shape or conformation, we need to understand these four levels of protein structure: primary, secondary, tertiary, and quaternary.
  • A protein's primary structure is the unique sequence of amino acids in each polypeptide chain that makes up the protein.
  • As a result, quaternary structure only applies to multi-subunit proteins; that is, proteins made from one than one polypeptide chain.