Difference Between Alpha and Beta Helix

Thekey differencebetween alpha and beta helix relies on the type of Hydrogen bonding they form in developing these structures.Alpha helices form分子内氢键而beta螺旋形成inter-molecular hydrogen bonds.

Complex proteins have four structural organizational levels – primary, secondary, tertiary and quaternary. The secondary structures of proteins form thepeptidechains in different orientations. The peptide chains consist of amino acid sequences bound by peptide bonds. Therefore, there are two main secondary structures in proteins as alpha helix and beta helix. In addition, there are other secondary structures called the beta turn and hairpin structures. Mainly, this article focuses on the difference between alpha and beta helix.

内容

1.Overview and Key Difference
2.What is Alpha Helix
3.什么是beta螺旋
4.Similarities Between Alpha and Beta Helix
5.Side by Side Comparison – Alpha vs Beta Helix in Tabular Form
6。概括

What is Alpha Helix?

Proteins have four structural levels of organization. Of these, the alpha helix is the commonest secondary structure of proteins. And, this structure appears as a rod that is wound around a central axis. Furthermore, the alpha helix is a right-handed helix. However, left-handed helices could also be present. Here, the peptide bonds form from the amino-terminal to the carboxy-terminal.氨基酸通过这些肽键相互联系. Intra-molecular hydrogen bonds are the main cause for forming the alpha helix.

Arrangement of the alpha helix depends on thehydrophilic and hydrophobicnature of the protein. If the amino acid sequence consists of a high number of hydrophilic R (variable) groups, the R groups orient to the aqueous phase. If the variable groups are hydrophobic, they will jut out to the hydrophobic phase of the environment. In either scenario, the R groups appear to extend out of the helical structure. Due to these structural characteristics, alpha helix is more resistant to mutations. Thus, the presence of Hydrogen bonds stabilizes the structure of the alpha helix. There is an average of 3.6 residues per turn in an alpha helix as it takes 3.6 residues for the hydrogen bonds to develop. Some structural proteins such as collagen and keratin are rich in alpha helices.

什么是beta螺旋？

β螺旋是蛋白质的第二大最常见的二级结构。尽管它不像α螺旋那样普遍，但β螺旋的存在在蛋白质结构中也起着重要作用。Beta螺旋的形成是通过以平行方式或反平行方式排列的两张Beta板进行的。这些床单然后形成螺旋结构。两张片链之间的分子间氢键有助于形成β螺旋。

Beta helices can be both right handed or left handed depending on their binding patterns. When forming a beta helix, the variable groups of the two beta sheets will arrange within the core of the helix. Therefore, the majority of the groups forming beta sheets have hydrophobic functions.

与Alpha螺旋相反，17个残留物在Beta螺旋中形成一个转弯。金属离子能够激活β螺旋的形成。与α螺旋相似，氢键支持以维持β螺旋的结构。碳酸酐酶和果胶裂解酶是两种富含β螺旋的蛋白质。

Alpha和Beta螺旋之间有什么相似之处？

• α和β螺旋是蛋白质的两个二级结构。
• 氨基酸是两个二级结构的单体。
• Furthermore, the chemical constituents of the alpha and beta helices are carbon, hydrogen, oxygen, nitrogen, and sulfur.
• Also, both secondary structures develop into a higher level organization.
• Moreover, both are stabilized by hydrogen bonds.
• 在这两个结构中，疏水性都取决于氨基酸的R组的存在。

α和β直升机之间的区别是什么x?

The key difference between the alpha and beta helix is the type of hydrogen bonding they show. Alpha helix shows intra-molecular hydrogen bonding while beta helix shows inter-molecular hydrogen bonding. In addition, the alpha helix forms a right-handed helix, while beta helix can form both right and left-handed helices. So, this is also a significant difference between alpha and beta helix.

此外，α和β螺旋之间的另一个区别在于，α螺旋形成是通过氨基酸序列的扭曲而发生的，而在β螺旋形成中，两个平行或反平行的两个β型β形成。

The below info-graphic presents more information regarding the difference between alpha and beta helix.

概括– Alpha vs Beta Helix

α螺旋和β螺旋对于识别和推导复杂的蛋白质结构都很重要。两种类型都是蛋白质的二级结构。然而，α螺旋是氨基酸序列的螺旋扭曲。相反，β螺旋形成是通过平行或反行β表的氢键进行的。此外，氢键是α螺旋形式的分子内分子，而氢键在β螺旋形式中为分子间。此外，这两个结构都有一个R组，它决定了蛋白质的疏水性。因此，这总结了Alpha和Beta螺旋之间的差异。

Reference:

1.“蛋白质结构的顺序”。可汗学院，可汗学院，Available here.
2. “Protein Secondary Structure: α-Helices and β-Sheets.” Structural Bioinformatics: Practical Guide,Available here.

Image Courtesy:

1. “Alpha beta structure (2)” By Thomas Shafee – Own work(CC BY-SA 4.0)viaCommons Wikimedia
2. “1m8n Choristoneura fumiferana” By WillowW at the English language Wikipedia(CC BY-SA 3.0)viaCommons Wikimedia