Determining Protein Sequences (AQA A Level Biology): Revision Note

Determining protein sequences

• The genome of simpler organisms can be used to obtain the proteome of the organism

• Large databases are created containing information about an organism's gene sequences and amino acid/protein sequences

• Once the genome is known, scientists can:

  • use bioinformatics to identify genes

  • predict the amino acid sequences of proteins

  • study which proteins are actively expressed in different conditions

• This information can be used for a range of applications

  • For example, identifying potential antigens for use in vaccine production

• Simpler organisms like bacteria and viruses are used. This is because they have:

  • smaller genomes

  • no introns (especially in prokaryotes)

  • less complex gene regulation

• This makes the genomes of simpler organisms easier to sequence and interpret than those of eukaryotes

Vaccine production

• Knowing the proteome of pathogens (like bacteria or viruses) enables scientists to identify antigens —the proteins on the surface of the pathogen that trigger an immune response

• This can be carried out as follows:

  • Sequence the genome of the pathogen

  • Use computational tools to predict the proteome (which proteins are made)

  • Identify proteins that:

    • Are found on the surface of the pathogen

    • Are unique to the pathogen (not found in humans)

    • Can stimulate an immune response

  • Use these proteins as antigens in vaccines

The Malaria vaccine

• Plasmodium falciparum is a species of parasite that causes severe forms of malaria

• Thousands of these parasites have been used for genome sequencing

• Scientists have been searching for differences between their DNA sequences to identify the genes that display the highest level of variation between individuals

  • A high level of variation suggests that those genes are under strong selective pressure. These genes could code for the antigen proteins found on the parasites

• Once the antigenic genes are identified, the antigen they code for can be used in vaccine production

  • RTS,S (Mosquirix) is the first malaria vaccine approved for human use

  • It targets a surface protein of Plasmodium falciparum; this antigen was identified using genomic and proteomic data from the parasite