The phrase "affect the function of the protein" is correct and usable in written English.
It can be used in scientific or technical contexts when discussing how certain factors influence the activity or behavior of a protein.
Example: "Mutations in the gene can significantly affect the function of the protein, leading to various health issues."
Alternatives: "influence the activity of the protein" or "impact the role of the protein."
The former leads to a basic amino acid at pH = 7 (serine), whereas the latter encodes a neutral amino acid (alanine) that may affect the function of the protein.
Using modern day synthetic technology, scientists can create thousands of slightly altered variants of the gene of interest, making random mutations throughout the gene or specifically at sites in the gene that they think will affect the function of the protein it encodes.
So far, scientists have found that different populations of living humans have inherited the Neandertal version of genes that cause diabetes, lupus, and Crohn's disease; alter immune function; and affect the function of the protein keratin in skin, nails, and hair.
The L124F and G194D changes occurred in a highly conserved amino acid positions and may therefore affect the function of the protein (Figure 2B, [59]).
The residue G194 is located in the inner face of the active site, and thus, a mutation at this position is predicted to affect the function of the protein (Figure 2C-E, amino acid indicated in red; [60]).
Likewise, the deletion or mutation of critical domains flanking the ATPase, such as the bromodomain in SWI/SNF, has been shown to affect the function of the protein in many instances [42], [43], [44].
Protein tyrosine sulfation is again known to affect the function of the target protein [161].
These genetic changes likely affect the function of the VP7 protein virulence.
Both are likely to affect the function of the XRCC1 protein.
There is good evidence that MTHFR Ala222Val directly affect the function of the expressed protein.
Koppers-Lalic, D. et al. Varicellovirus UL49.5 proteins differentially affect the function of the transporter associated with antigen processing, TAP.
