biology

Microtubule plus-end tracking protein

Microtubule plus-end tracking protein is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Microtubule plus-end tracking protein rather than just read about it. In short: Microtubule plus-end/positive-end tracking proteins or +TIPs are a type of microtubule associated protein (MAP) which accumulate at the plus ends of microtubules. +TIPs are arranged in diverse groups which are classified based on their structural components; however, all classifications are distinguished by their specific accumulation at the plus end of microtubules and their ability to maintain interactions between…

Key takeaways

Microtubule plus-end tracking protein belongs to biology; place it in that map before memorising details.
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Connect Microtubule plus-end tracking protein to a quantity you can measure, compute or draw — that is where exam questions come from.
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Reference excerpt

Microtubule plus-end/positive-end tracking proteins or +TIPs are a type of microtubule associated protein (MAP) which accumulate at the plus ends of microtubules. +TIPs are arranged in diverse groups which are classified based on their structural components; however, all classifications are distinguished by their specific accumulation at the plus end of microtubules and their ability to maintain interactions between themselves and other +TIPs regardless of type. +TIPs can be either membrane bound or cytoplasmic, depending on the type of +TIPs. Most +TIPs track the ends of extending microtubules in a non-autonomous manner.

Regulation of microtubule dynamics +TIPs' localization at the plus end of microtubules is a highly relevant aspect of microtubule regulation. A +TIP may promote microtubule growth by catalyzing the addition of tubulin at the plus end, or it may balance microtubules at the cell cortex. Many mechanisms of regulation are not fully understood. In mitosis, +TIPs allocate microtubule addition and promote dynamical regulation at mitotic kinetochores. They also contribute to the extension of endoplasmic reticulum tubules at expanding microtubule ends. Furthermore, +TIPs aid in advocating organization of specialized microtubule arrays (an oft-cited example being the discrete arrangement of bipolar microtubule bundles in fission yeast).

In addition to the basic known functions of +TIPs, the proteins are crucial for the linkages between microtubule ends and other cellular structures. +TIPs can bind microtubule ends to the cell cortex by colliding to plasma membrane-associated proteins or in the case of some +TIPs, directly to the actin fiber. Moreover, +TIP complexes in budding yeast are utilized for myosin-based transport of microtubule ends. Microtubule plus-end trafficking proteins engage in microtubule actin crosstalk, such as the CLIP-170 (+TIP) that controls actin polymerization—a necessity in mammalian phagocytosis. +TIPs have been known for an extravagant accumulation by the centrosomes and other structural organizing centers of cells. This leads to the basic assumption that +TIPs may aid in microtubule nucleation and anchoring; however, its distinct role at centrosomes still awaits evidential findings. Overall, +TIPs play a critical part in morphogenesis, cell division, and motility.

Classifications of +TIPs based on structural domains About 20 different families of microtubule plus-end trafficking proteins (+TIPs) have been discovered since the first finding of +TIP CLIP-170 (CLIP1) in 1999. Since then +TIPs have been studied thoroughly and still are. The largest group of +TIPs contain complex and large proteins which have low-complexity sequence areas which are affluent in standard proline and serine residues. These types of proteins share a structural basic Ser-X-lle-Pro (where X can be any amino acid). This certain “code” allows these specific complex proteins to be recognizable to another family of +TIPs, known as the EB proteins. The end-binding proteins (EB proteins), have a precise N-terminal domain which is accountable for microtubule binding. The C-terminus however, sustains an alpha-helical coiled region which regulates parallel dimerization of EB monomers and comprises an acidic tail (attaining EEY/F motif) along with an EB homology domain (EBH). The EBH domain and or the EEY/F motif allow the EB proteins to physically interrelate with an array of +TIP in order to recruit them to microtubule ends. Other classes of +TIPs include the cytoskeleton-associated proteins which are known for their glycine rich domain and a special conserved hydrophobic cavity which permits them to confer interactions with microtubules and EB proteins. There is also a class of +TIPs which substantiates a TOG domain. TOG domains mediate tubulin binding and are important for microtubule growth correlated activity. Basically, the brief classification of +TIPs can be made prior to the specific domain and function rudiments of the particular protein; there exist many more +TIPs, but these correspond to the main oriented and highly studied +TIPs.

EB Proteins

EB1 and other proteins SxlP proteins

APC MACF STIM1 TOG proteins

XMAP215 CLASP Motor proteins

Tea2 MCAK Dynein HC Other proteins Dam1 Lis1 Kar9

Types of +TIPs related to specific functions

Used in Catastrophe: MCAK Used in Rescue: CLIP-170 CLASP Stabilization: CLASP APC MACF Polymerization: EB1 XMAP215 Depolymerization: MCAK

Communication with cellular components (+TIPs that interact with the specified structure): Centrosomes

XMAP215 EB1 CLASP APC LIS1 FOP Dynein Dynactin CDK5RAP2 Microtubules

Ncd Klp2 Endoplasmic Reticulum

EB1 STIM1 F-actin

MACF APC CLASP CLIP-170 Kar9 RhoGEF2 p140Cap

Vesicles

Dynein CLIP-170 Dynactin Melanophilin Kinetochores

Dam1 CLASP CLIP-170 APC EB1 MCAK LIS1 Dynein Dynactin Cortex of the cell

CLASP APC MACF CLIP-170 EB1 LIS1 Dynein Dynactin

Expanding the study of +TIPs Scientists continue to further their understanding of certain mechanisms done by +TIPs and the range of different types of these proteins. Understanding of microtubule plus-end trafficking proteins has greatly expanded since the discovery of CLAP1, and surely will continue to expand as predicted by many researchers and cytologists. Currently, +TIPs may play critical roles in more than just the general aspects known; also with other particular cell structures along with the known structures which are the endoplasmic reticulum, F-actin, vesicles, microtubules, kinetochores, cell cortex, and centrosomes.

Illustrations

Worked examples

Example 1 — a first encounter with Microtubule plus-end tracking protein

Start with the simplest possible case. Write down what Microtubule plus-end tracking protein claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Microtubule plus-end tracking protein before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Microtubule plus-end tracking protein ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Microtubule plus-end tracking protein

In research: Microtubule plus-end tracking protein appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Microtubule plus-end tracking protein in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Microtubule plus-end tracking protein is common in secondary-school and first-year university syllabi. It links to neighbouring topics Proteins, so understanding it makes those chapters shorter.
In everyday life: Look for Microtubule plus-end tracking protein outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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Frequently asked questions

What is Microtubule plus-end tracking protein in simple terms?

Why does Microtubule plus-end tracking protein matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

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Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

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