8.3.2 Determining Protein Sequences

What Are Protein Sequences?

Protein sequences refer to the specific order of amino acids in a polypeptide chain, determined by the sequence of bases in DNA.

Using Genomic Information to Determine Protein Sequences

1. Reading the Genome:

• By sequencing the DNA of an organism, scientists can identify the genes that code for proteins.
• The sequence of bases in a gene is transcribed into mRNA and then translated into a sequence of amino acids.

2. Determining the Proteome:

• In simpler organisms (e.g., bacteria), identifying the proteome (all the proteins produced) is straightforward as most of the genome is coding DNA.
• In complex organisms like humans, non-coding DNA and regulatory sequences complicate the process.

3. Predicting Amino Acid Sequences:

• Advances in bioinformatics enable the identification of coding sequences (exons) in the genome.
• Once the coding sequence is known, the genetic code is used to predict the sequence of amino acids in the protein.

4. Applications:

• Identifying proteins involved in disease pathways for the development of targeted therapies.
• Understanding protein function to improve agriculture, biotechnology, and medicine.

Challenges in Complex Organisms

1. Non-Coding DNA:

• Much of the human genome consists of introns, regulatory regions, or repetitive sequences that do not code for proteins.

2. Alternative Splicing:

• A single gene can produce multiple proteins due to the process of alternative splicing, where exons are rearranged during mRNA processing.

3. Post-Translational Modifications:

• Proteins can undergo changes after synthesis (e.g., phosphorylation, glycosylation), which cannot be predicted from the DNA sequence alone.