biology

Potassium uptake permease

Potassium uptake permease 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 Potassium uptake permease rather than just read about it. In short: The potassium (K+) uptake permease (KUP) family (TC# 2.A.72) is a member of the APC superfamily of secondary carriers. Proteins of the KUP/HAK/KT family include the KUP (TrkD) protein of E. coli and homologues in both Gram-positive and Gram-negative bacteria.

Key takeaways

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

Reference excerpt

The potassium (K+) uptake permease (KUP) family (TC# 2.A.72) is a member of the APC superfamily of secondary carriers. Proteins of the KUP/HAK/KT family include the KUP (TrkD) protein of E. coli and homologues in both Gram-positive and Gram-negative bacteria. High affinity (20 μM) K+ uptake systems (Hak1, TC# 2.A.72.2.1) of the yeast Debaryomyces occidentalis as well as the fungus, Neurospora crassa, and several homologues in plants have been characterized. Arabidopsis thaliana and other plants possess multiple KUP family paralogues. While many plant proteins cluster tightly together, the Hak1 proteins from yeast as well as the two Gram-positive and Gram-negative bacterial proteins are distantly related on the phylogenetic tree for the KUP family. All currently classified members of the KUP family can be found in the Transporter Classification Database.

Structure and function

Escherichia coli The E. coli protein is 622 amino acyl residues long and has 12 established transmembrane spanners (440 residues) with a requisite hydrophilic, C-terminal domain of 182 residues, localized to the cytoplasmic side of the membrane. Deletion of most of the hydrophilic domain reduces but does not abolish KUP transport activity. The function of the C-terminal domain is not known. The E. coli KUP protein is believed to be a secondary transporter. Uptake is blocked by protonophores such as CCCP (but not arsenate), and evidence for a proton symport mechanism has been presented. The N. crassa protein was earlier shown to be a K+:H+ symporter, establishing that the KUP family consists of secondary carriers.

Yeast The yeast high affinity (KM = 1 μM) K+ transporter Hak1 is 762 amino acyl residues long with 12 putative TMSs. Like the E. coli KUP protein, it possesses a C-terminal hydrophilic domain, probably localized to the cytoplasmic side of the membrane. Hak1 may be able to accumulate K+ 106-fold against a concentration gradient. The plant high and low affinity K+ transporters can complement K+ uptake defects in E. coli.

TRK TRK transporters, responsible for the bulk of K+ accumulation in plants, fungi, and bacteria, mediate ion currents driven by the large membrane voltages (-150 to -250 mV) common to non-animal cells. Bacterial TRK proteins resemble K+ channels in their primary sequence, crystallize as membrane dimers having intramolecular K+-channel-like folding, and complex with a cytoplasmic collar formed of four RCK domains. Fungal TRK proteins possess a large built-in regulatory domain and a highly conserved pair of transmembrane helices (TMSs 7 and 8, ahead of the C-terminus), postulated to facilitate intramembranal oligomerization. These fungal HAK proteins are chloride channels mediating efflux, a process suppressed by osmoprotective agents. It involve hydrophobic gating and resembles conduction by Cys-loop ligand-gated anion channels. Possibly, the tendency of hydrophobic or amphipathic transmembrane helices to self-organize into oligomers creates novel ionic pathways through membranes: hydrophobic nanopores, pathways of low selectivity governed by the chaotropic behavior of individual ionic species under the influence of membrane voltage.

Transport reaction The generalized transport reaction for members of the KUP family is:

K+ (out) + energy → K+ (in).

See also Transporter Classification Database Membrane transport protein

References

Worked examples

Example 1 — a first encounter with Potassium uptake permease

Start with the simplest possible case. Write down what Potassium uptake permease 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 Potassium uptake permease 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 Potassium uptake permease 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 Potassium uptake permease

In research: Potassium uptake permease 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 Potassium uptake permease 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: Potassium uptake permease is common in secondary-school and first-year university syllabi. It links to neighbouring topics Protein families, Solute carrier family, so understanding it makes those chapters shorter.
In everyday life: Look for Potassium uptake permease 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 Potassium uptake permease in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Potassium uptake permease 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 Potassium uptake permease out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Potassium uptake permease in simple terms?

Why does Potassium uptake permease 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 Potassium uptake permease?

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 Potassium uptake permease.