Editing Protein folding (section)

=== Primary structure ===
{{Main|Protein primary structure}}

The primary structure of a protein, its linear amino-acid sequence, determines its native conformation.<ref name="Anfinsen1">{{cite journal | vauthors = Anfinsen CB | title = Principles that govern the folding of protein chains | journal = Science | volume = 181 | issue = 4096 | pages = 223–30 | date = July 1973 | pmid = 4124164 | doi = 10.1126/science.181.4096.223 | bibcode = 1973Sci...181..223A }}</ref> The specific amino acid residues and their position in the polypeptide chain are the determining factors for which portions of the protein fold closely together and form its three-dimensional conformation. The amino acid composition is not as important as the sequence.<ref name="Voet_2016">{{cite book | title = Principles of Biochemistry | first1 = Donald | last1 = Voet | first2 = Judith G. | last2 = Voet | first3 = Charlotte W. | last3 = Pratt | name-list-style = vanc | publisher = Wiley | year = 2016 | edition = Fifth | isbn = 978-1-118-91840-1 }}</ref> The essential fact of folding, however, remains that the amino acid sequence of each protein contains the information that specifies both the native structure and the pathway to attain that state. This is not to say that nearly identical amino acid sequences always fold similarly.<ref>{{cite journal | vauthors = Alexander PA, He Y, Chen Y, Orban J, Bryan PN | title = The design and characterization of two proteins with 88% sequence identity but different structure and function | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 104 | issue = 29 | pages = 11963–8 | date = July 2007 | pmid = 17609385 | pmc = 1906725 | doi = 10.1073/pnas.0700922104 | bibcode = 2007PNAS..10411963A | doi-access = free }}</ref> Conformations differ based on environmental factors as well; similar proteins fold differently based on where they are found.