biology

UQCC3

UQCC3 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 UQCC3 rather than just read about it. In short: Ubiquinol-cytochrome c reductase complex assembly factor 3 is a protein that in humans is encoded by the UQCC3 gene. Located in mitochondria, this protein is involved in the assembly of mitochondrial Complex III, stabilizing supercomplexes containing Complex III.

Key takeaways

UQCC3 belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect UQCC3 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of UQCC3 from memory before moving on to harder problems.

Reference excerpt

Ubiquinol-cytochrome c reductase complex assembly factor 3 is a protein that in humans is encoded by the UQCC3 gene. Located in mitochondria, this protein is involved in the assembly of mitochondrial Complex III, stabilizing supercomplexes containing Complex III. Mutations in the UQCC3 gene cause Complex III deficiency with symptoms of hypoglycemia, hypotonia, lactic acidosis, and developmental delays. This protein plays an important role as an antiviral factor, bolstering the ability of cells to inhibit viral replication, independent of interferon production. The UQCC3 protein can be cleaved by OMA1 metalloprotease during mitochondrial depolarization, targeting the cell for apoptosis. Depletion of this protein alters cardiolipin composition, causing cellular and mitochondrial defects.

Structure The UQCC3 gene is located on the q arm of chromosome 11 in position 12.3 and spans 2,036 base pairs. The gene produces a 10.1 kDa protein composed of 93 amino acids. This protein faces the intermembrane space. It possesses an N-terminal signal peptide and a signal transmembrane structure, in addition to several phosphorylation sites. The secondary structure of this protein is made up mostly of random coils and alpha helices. Alpha helices 2 and 3 bind to cardiolipin.

Function The UQCC3 gene encodes a protein that functions in complex III assembly, downstream of assembly factors UQCC1 and UQCC2. This is evidenced by the observation that UQCC3 levels are reduced in cells with decreased levels of UQCC1 and UQCC2, but lack of the UQCC3 protein does not affect levels of UQCC1 and UQCC2. Predicted to be a secretary protein with small molecular weight, this protein has important functions in cellular proliferation and antiviral innate immune regulation. Expression of this protein is ubiquitous in carcinomas, along with normal tissues. During the early stages of Complex III assembly, the UQCC3 protein stabilizes supercomplexes containing Complex III, most notably the III2/IV supercomplex.

Clinical Significance In the sole recorded case of a mutation in the UQCC3 gene, a patient with a homozygous missense mutation presented with nuclear type 9 complex III deficiency, displaying symptoms of hypoglycemia, hypotonia, lactic acidosis, severe delayed psychomotor development, and other developmental delay. The patient also had decreased levels of cytochrome b within Complex III. The UQCC3 protein also has a role as an antiviral factor, independent of interferon production. Levels of this protein increase in response to a viral infection, improving the ability of cells to inhibit viral replication. Overexpression of the UQCC3 gene increases transcription of OAS3 while knockdown of RNase L or OAS3 hampers the antiviral effect of UQCC3. Signaling from UQCC3 to the OAS-RNase L system is independent of interferon production. This protein is also regulated by expression of the double-stranded RNA-dependent protein kinase EIF2AK2. Depleted levels of the UQCC3 protein cause impaired respiration and subtle yet significant alterations in cardiolipin composition, which then result in abnormal crista morphology, increased sensitivity to apoptosis, and decreased levels of ATP. Furthermore, mitochondrial depolarization causes OMA1 metalloprotease to cleave the UQCC3 protein; effectively, this mechanism targets cells with damaged mitochondria for apoptosis.

Interactions This protein associates with the rest of mitochondrial Complex III and has protein-protein interactions with PHLDA3.

References

Illustrations

Worked examples

Example 1 — a first encounter with UQCC3

Start with the simplest possible case. Write down what UQCC3 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 UQCC3 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 UQCC3 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 UQCC3

In research: UQCC3 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 UQCC3 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: UQCC3 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Genes on human chromosome 11, Human proteins, Mitochondrial proteins, so understanding it makes those chapters shorter.
In everyday life: Look for UQCC3 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 UQCC3 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what UQCC3 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 UQCC3 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is UQCC3 in simple terms?

Why does UQCC3 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 UQCC3?

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 UQCC3.