The key difference between Alpha and Beta Tubulin is that the alpha tubulin contains Asp-254 at the E-site while the beta-tubulin contains Lys-254 at the N-site. Apart from that, GTP is always attached to alpha-tubulin subunit, while at the beta-tubulin subunit, GTP is exchangeable for the microfilaments to polymerize.
Microtubules are a part of the cytoskeleton of the eukaryotic cell cytoplasm. Therefore, microtubules exist as a network of protein filaments distributed throughout the cell providing a definite shape to cell and keeping the organelles in place. Moreover, they are composed of two main tubulin proteins namely alpha and beta tubulins. Alpha and beta are two families of eukaryotic tubulin superfamily. Alpha and beta tubulin exists as a dimer, and it is the basic building block of microtubules.
CONTENTS
1. Overview and Key Difference
2. What is Alpha Tubulin
3. What is Beta Tubulin
4. Similarities Between Alpha and Beta Tubulin
5. Side by Side Comparison – Alpha vs Beta Tubulin in Tabular Form
6. Summary
What is Alpha Tubulin?
Alpha-tubulin is one type of globular tubulin protein, which is a component of the basic building block of the microtubule. Alpha-tubulin makes a dimer with beta-tubulin.
Figure 01: Tubulin Dimer
Furthermore, its weight is approximately 55 kDa and has an isoelectric point of 4.1. Alpha tubulin has Asp-254 at the E-site and GTP always attached to it.
What is Beta Tubulin?
Beta-tubulin is a type of tubulin that involves making dimmers in microtubules. It has a similar weight and isoelectric point with that of the alpha tubulin.
Figure 02: Beta Tubulin
However, in N-site of the beta-tubulin, there is Lys-254. And also GTP and GDP are exchangeable in beta-tubulin.
What are the Similarities Between Alpha and Beta Tubulin?
- Alpha and beta tubulins have alpha helices, beta sheets and random protein coils.
- They are the components of microtubules.
- Both tubulins undergo isotypic forms.
- Post-translational modifications can be there in both tubulins.
- Both the tubulins share sequence homology.
- They both have a mass of around 50 kDa.
- Alpha and Beta Tubulin proteins polymerize into microtubules.
- Both bind with GTP.
What is the Difference Between Alpha and Beta Tubulin?
Alpha tubulin and beta tubulin are two proteins, which are components of the microtubules. They share similar weight and isoelectric points. However, their N-site and E-site are different. At the E-site of the alpha tubulin, there is an Asp-254. At the N-site of beta-tubulin, there is a Lys-254. This is the key difference between alpha and beta tubulin. Furthermore, the GTP is always attached to alpha tubulin while GTP-GDP is exchangeable at beat tubulin.
Summary – Alpha vs Beta Tubulin
The alpha and beta tubulins are two globular proteins that make the alpha beta dimer in microtubules. Therefore, Alpha and beta tubulin dimer is the basic building block of microtubules. Moreover, alpha tubulin contains Asp-254 at the E-site while beta-tubulin contains Lys-254 at the N-site. Furthermore, alpha and beta tubulin differ from the GTP attachment. GTP is always attached to alpha tubulin subunit, while at the beta-tubulin subunit, GTP is exchangeable for the microfilaments to polymerize. This is the difference between alpha and beta tubulin.
Reference:
1.“Αβ Tubulin (PDB ID: 1jff) from Bos Taurus.” Αβ Tubulin, Young Jun Lee. Available here
2.“Tubulin.” Wikipedia, Wikimedia Foundation, 18 July 2018. Available here
Image Courtesy:
1.’Tubulin dimer 1JFF’By Thomas Splettstoesser – Own work (CC BY-SA 4.0) via Commons Wikimedia
2.’Microtubule structure’By Thomas Splettstoesser – Own work (CC BY-SA 4.0) via Commons Wikimedia