Secondary structure
Secondary structure
The Secondary structure (pronunciation: /ˈsɛkəndɛri ˈstrʌktʃər/) is a term used in Biochemistry and Molecular Biology to describe the specific three-dimensional form of local segments of biopolymers such as proteins and nucleic acids (DNA/RNA).
Etymology
The term "Secondary structure" is derived from the fact that this structure is the second level of organization of protein and nucleic acid structures, following the primary structure which is the linear sequence of amino acids or nucleotides.
Types of Secondary Structures
In proteins, the secondary structure includes alpha helices, beta sheets, and turns. In nucleic acids, it includes features such as stem-loops and hairpins.
Alpha Helix
The alpha helix (pronunciation: /ˈælfə ˈhiːlɪks/) is a right-handed coiled or spiral conformation, in which every backbone N-H group donates a hydrogen bond to the backbone C=O group of the amino acid located three or four residues earlier along the protein sequence.
Beta Sheet
The beta sheet (pronunciation: /ˈbiːtə ʃiːt/) is a protein secondary structure, in which beta strands are aligned alongside each other, forming a sheet-like structure held together by backbone hydrogen bonds.
Turns
Turns are short sequences of amino acids that allow the protein chain to reverse direction. They play a crucial role in enabling the formation of compact, globular protein structures.
Related Terms
- Tertiary structure: The overall three-dimensional structure of a biopolymer, resulting from interactions between secondary structural elements.
- Quaternary structure: The arrangement of multiple folded protein or nucleic acid molecules in a multi-subunit complex.
External links
- Medical encyclopedia article on Secondary structure
- Wikipedia's article - Secondary structure
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