Human proteins are created through a process called translation, where amino acids are linked together following the instructions encoded in messenger RNA (mRNA) molecules. These mRNA molecules are initially transcribed from DNA within the cell's nucleus. This intricate process occurs on ribosomes, located in the cell's cytoplasm.
The Protein Synthesis Process: A Step-by-Step Overview
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Transcription: The process begins in the cell nucleus. DNA, containing the genetic blueprint, is transcribed into mRNA. This mRNA molecule carries the genetic code for a specific protein.
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mRNA Movement: The newly formed mRNA molecule moves out of the nucleus and into the cytoplasm.
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Translation: In the cytoplasm, the mRNA molecule binds to a ribosome. The ribosome reads the mRNA's genetic code, determining the sequence of amino acids needed for the protein.
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Amino Acid Assembly: Transfer RNA (tRNA) molecules bring specific amino acids to the ribosome based on the mRNA's instructions. The ribosome then links these amino acids together, forming a polypeptide chain.
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Protein Folding: Once the polypeptide chain is complete, it folds into a specific three-dimensional structure. This structure is crucial for the protein's function. This folding is influenced by various factors including interactions between amino acids and the cellular environment.
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Protein Modification (Optional): Some proteins undergo further modifications after folding, such as glycosylation (addition of sugar molecules) or phosphorylation (addition of phosphate groups). These modifications can alter the protein's function or stability.
Methods for Human Protein Production: Examples from Research
Several techniques are employed to produce human proteins for research and other applications. Examples include:
- Cell-free systems: These systems, such as the wheat cell-free protein production system, allow for the production of large quantities of recombinant human proteins (e.g., CF-PA2Vtech created an array of 19,712 recombinant human proteins).
- Cell-based systems: Mammalian cell lines can be used to produce human proteins, particularly for vaccines. (Note: Some vaccines utilize human embryo cells, raising ethical concerns regarding the presence of fetal cell proteins in the final product).
- High-throughput production: Methods are being developed to allow for efficient, large-scale production of human proteins for applications like structural studies (e.g., the Structural Genomics Consortium's (SGC) success in purifying 48% of attempted human proteins).
- Tissue Microarrays: This technique, used in the Human Protein Atlas project, analyzes protein expression patterns in normal human tissues, cancer, and cell lines, offering insights into protein function and disease.
The Human Protein Atlas is a notable initiative mapping all human proteins across various cells, tissues, and organs. This project provides valuable data about protein localization and expression levels across the human body. Understanding human protein production and function is crucial for advancements in medicine and biotechnology.
