biology

Prokaryotic riboflavin biosynthesis protein

Prokaryotic riboflavin biosynthesis 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 Prokaryotic riboflavin biosynthesis protein rather than just read about it. In short: The prokaryotic riboflavin biosynthesis protein is a bifunctional enzyme found in bacteria that catalyzes the phosphorylation of riboflavin into flavin mononucleotide (FMN) and the adenylylation of FMN into flavin adenine dinucleotide (FAD). It consists of a C-terminal riboflavin kinase and an N-terminal FMN-adenylyltransferase.

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Reference excerpt

The prokaryotic riboflavin biosynthesis protein is a bifunctional enzyme found in bacteria that catalyzes the phosphorylation of riboflavin into flavin mononucleotide (FMN) and the adenylylation of FMN into flavin adenine dinucleotide (FAD). It consists of a C-terminal riboflavin kinase and an N-terminal FMN-adenylyltransferase. This bacterial protein is functionally similar to the monofunctional riboflavin kinases and FMN-adenylyltransferases of eukaryotic organisms, but only the riboflavin kinases are structurally homologous.

Structure Prokaryotic riboflavin biosynthesis proteins are also known as the prokaryotic type-I FAD synthetases, which consist of a C-terminal riboflavin kinase (RFK) and an N-terminal FMN-adenylyltransferase (FMNAT). The globular RFK consists of six antiparallel β-sheets that form a β-barrel, and an α-helix adjacent to this structure. The barrel and helix are held together by 7 independent loops. The FMNAT module contains an α/β dinucleotide binding domain within the active site, which it uses to bind to the substrate. The overall structure is held together by 5 parallel β-sheets that are adjacent to 4 α-helices, with 2 being long and 2 being short. A subdomain, containing 2 smaller α-helices, encompasses the area that connects to the C-terminal RFK module.

Mechanism Riboflavin is converted into catalytically active cofactors FAD and FMN by the actions of riboflavin kinase EC 2.7.1.26, which converts it into FMN, and FAD synthetase EC 2.7.7.2, which adenylates FMN to FAD. The RFK module phosphorylates the riboflavin substrate and converts it into FMN, which is then released from the module. This reaction is dependent on an ATP molecule stabilized by an Mg2+ ion, which causes only a single phosphate group to leave the ATP and bond to riboflavin. The released FMN then joins to the N-terminal FMNAT module and is adenylated, with the adenylyl group of ATP attaching to the phosphate group on FMN and the diphosphate group leaving. ATP + riboflavin ⇌ ADP + FMN ATP + FMN ⇌ diphosphate + FAD

Phylogenetic Domain Comparison Eukaryotes usually have two separate enzymes, while most prokaryotes have a single bifunctional protein that can carry out both catalyses, although exceptions occur in both cases. While eukaryotic monofunctional RFK is orthologous to the bifunctional prokaryotic RFK module, the monofunctional FMNAT differs from its prokaryotic counterpart, and is instead related to the PAPS-reductase family. The bacterial FMNAT module of the bifunctional enzyme has remote similarity to eukaryotic nucleotidyltransferases and, hence, it may be involved in the adenylylation reaction of FAD synthetases.

References

Illustrations

Worked examples

Example 1 — a first encounter with Prokaryotic riboflavin biosynthesis protein

Start with the simplest possible case. Write down what Prokaryotic riboflavin biosynthesis 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 Prokaryotic riboflavin biosynthesis 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 Prokaryotic riboflavin biosynthesis 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 Prokaryotic riboflavin biosynthesis protein

In research: Prokaryotic riboflavin biosynthesis 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 Prokaryotic riboflavin biosynthesis 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: Prokaryotic riboflavin biosynthesis protein is common in secondary-school and first-year university syllabi. It links to neighbouring topics Protein families, so understanding it makes those chapters shorter.
In everyday life: Look for Prokaryotic riboflavin biosynthesis 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

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