biology

OST Family

OST Family 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 OST Family rather than just read about it. In short: Members of the organic solute transporter (OST) family (TC# 2.A.82) (Slc51 genes) have been characterized from a small bottom feeding species of fish called the little skate, Raja erinacea. Members have also been characterized from humans and mice.

Key takeaways

OST Family belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect OST Family to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of OST Family from memory before moving on to harder problems.

Reference excerpt

Members of the organic solute transporter (OST) family (TC# 2.A.82) (Slc51 genes) have been characterized from a small bottom feeding species of fish called the little skate, Raja erinacea. Members have also been characterized from humans and mice. The OST family is a member of the larger group of secondary carriers, the APC superfamily.

Substrates Substrates for OST transporters include a variety of organic compounds, most being anionic. Transport of estrone sulfate by the two subunit Ost transporter of Raja erinacea (TC# 2.A.82.1.1) is Na+-independent, ATP-independent, saturable and inhibited by other steroids and anionic drugs. Bile acids such as taurocholate as well as digoxin and prostaglandin E2 are substrates of this system, while estradiol 17β-D-glucuronide and p-aminohippurate are apparently not. Mammalian homologues (e.g., 2.A.82.1.2) similarly exhibit broad substrate specificity, transporting the same compounds, possibly by an anion:anion exchange mechanism.

Transport reaction The generalized transport reaction catalyzed by OSTα/OSTβ is:

organic anion (out) ⇌ organic anion (in)

Structure Each transport system consists of two polypeptide chains, designated α and β. For the human protein (TC# 2.A.82.1.2), the α-subunit is of 340 amino acyl residues (aas) with 7 putative transmembrane segments (TMSs) while the β-subunit is of 128 aas with 1 putative TMS near the N-terminus (residues 40-56). Neither OSTα nor OSTβ alone has activity, both serving not only for heterodimerization and trafficking but also for function. The two proteins are highly expressed in many human tissues. The β-subunit is not required to target the α-subunit to the plasma membrane, but coexpression of both genes is required to convert OSTα to the mature glycosylated protein in enterocyte basolateral membranes and possibly for trafficking through the golgi apparatus. OSTαβ proteins are made in a variety of tissues including the small intestine, colon, liver, biliary tract, kidney, and adrenal gland. In polarized epithelial cells, they are localized to the basolateral membrane and function in the export or uptake of bile acids and steroids. Homologues of OSTα are found in many eukaryotes including animals (both vertebrates and invertebrates), plants, fungi and slime molds. Homologues of OSTβ are found only in vertebrate animals.

Crystal structures As of early 2016, no crystal structures had been determined. However, bioinformatics utilizing combinations of homology modelling and mutation experiments have been used to explore the heterdimer nature of the system as well as the mechanisms of substrate recognition and transport.

Worked examples

Example 1 — a first encounter with OST Family

Start with the simplest possible case. Write down what OST Family 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 OST Family 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 OST Family 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 OST Family

In research: OST Family 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 OST Family 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: OST Family is common in secondary-school and first-year university syllabi. It links to neighbouring topics Enzymes of known structure, Integral membrane proteins, Membrane proteins, so understanding it makes those chapters shorter.
In everyday life: Look for OST Family 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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How to study OST Family in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what OST Family means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain OST Family out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is OST Family in simple terms?

Why does OST Family 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.

How should I study OST Family?

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.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on OST Family.