Conservative Amino Acid Substations in Proteins Flashcards
How we use our knowledge of amino acid structure in genetics
- important in genomic sequencing an analysis
- function and evolution of proteins due to comparative sequences of nucleic acids to deduce sequences of proteins.
Conservative
unlikely to result in major change of the characteristics of a protein.
Acidic R group conservations
- Asp (D) and Glu (E)
Basic R group conservations
- Lys (K), Arg (R), and His (H)
Hydrophobic R group conservations
- Leu (L), Ile (I), Val (V)
- about the same size
Amide R group conservations
- Asn (N) and Gln (Q)
Aromatic group conservations
- Phe (F), Tyr (Y), and Trp (W)
Conservation on a genetic basis
- Many (but not all) amino substations that are conservative on a structural basis and also conservative on a genetic basis.
- They can result from the change of a single nucleotide in the third position of the codon.
Conservation on a genetic basis example
- Asp (D) GA U/C
- Glu (E) GA A/G
Aligning conserved sequences
- clone
- sequence
- BLAST
- align with CLUSTAL
BLAST
- find homology of protein
- determine hypothetical gene or actual gene
DNA polymerases
- proofread
Taq polymerases
- makes more mistakes
- fidelity
conservative substations on the frequency of substitution basis
- if one AA substitutes for another at a frequency higher than expected by chance = conservative
- determined statistically
BLAST
peptide or nucleic acid sequence and want to find what known proteins or nucleic acids have the sequence or related sequences.
CLUSTAL
- 2 or more proteins or nucleic acid sequences and you want to align them with the best fit.
strongly conserved versus structurally conserved substitutions
- are the same but 5 additional indications of homology in weakly conserved substitutions
Effect of non-conservative amino acid substitutions
- Normal erythrocytes versus sickle-cell anemia erythrocytes
- a homozygous mutation that changes Glutamic Acid (a very hydrophilic amino acid) to Valine (a very hydrophobic amino acid)
