biology

Phage r1t holin family

Phage r1t holin 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 Phage r1t holin family rather than just read about it. In short: The Lactococcus lactis Phage r1t Holin (r1t Holin) Family (TC# 1.E.18) is a family of putative pore-forming proteins that typically range in size between about 65 and 95 amino acyl residues (aas) in length, although a few r1t holins have been found to be significantly larger (i.e., 168 aa, 4 TMS, uncharacterized holin of Rhodococcus opacus; TC# 1.E.18.1.9). Phage r1t holins exhibit between 2 and 4 transmembrane segm…

Key takeaways

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Reference excerpt

The Lactococcus lactis Phage r1t Holin (r1t Holin) Family (TC# 1.E.18) is a family of putative pore-forming proteins that typically range in size between about 65 and 95 amino acyl residues (aas) in length, although a few r1t holins have been found to be significantly larger (i.e., 168 aa, 4 TMS, uncharacterized holin of Rhodococcus opacus; TC# 1.E.18.1.9). Phage r1t holins exhibit between 2 and 4 transmembrane segments (TMSs), with the 4 TMS proteins resulting from an intragenic duplication of a 2 TMS region. A representative list of the proteins belonging to the r1t holin family can be found in the Transporter Classification Database.

Function and expression The Lactococcus lactis phage r1t genome includes two adjacent genes, orf48 and orf49, which encode Orf48 (TC# 1.E.18.1.1; 75 aas) and a lysin Orf49 (270 aas), probably an N-acetyl-muramoyl-L-alanine amidase, respectively. Orf48 exhibits 2 putative hydrophobic transmembrane segments (TMSs) separated by a short β-turn region. It also has a hydrophobic N-terminus and a highly charged C-terminus. Orf48/Orf49 constitute the phage r1t lysis cassette. An essential role of Orf49 in cell lysis by Orf48 has been demonstrated. Orf48 is homologous to the Gp4 holin of Mycobacterium phage Ms6 (TC# 1.E.18.1.2). Like most double-stranded (ds) DNA phages, mycobacteriophage Ms6 uses the holin-endolysin system to achieve lysis of its host. In addition to endolysin (lysA) and holin (hol) genes, Ms6 encodes three accessory lysis proteins. The lysis function of Gp1, encoded by the gp1 gene that lies immediately upstream of lysA, was revealed. Catalão et al. observed Escherichia coli lysis after coexpression of LysA and Gp1 in the absence of the Ms6 holin. Gp1 does not belong to the holin class of proteins, but it shares several characteristics with molecular chaperones. The authors suggest that Gp1 interacts with LysA, and that this interaction is necessary for LysA delivery to its target. PhoA fusions showed that in Mycobacterium smegmatis, LysA is exported to the extracytoplasmic environment in the presence of Gp1 which is necessary for efficient M. smegmatis lysis, as Ms6 gp1 deletion results in host lysis defects. Catalao et al. proposed that delivery of Ms6 endolysin to the murein layer is assisted by Gp1, a chaperone-like protein, in a holin-independent manner.

The transport reaction catalyzed by phage r1t Orf48 is:lysin (in) → lysin (out)

See also Holin Lysin Transporter Classification Database

Further reading Catalão, Maria João; Gil, Filipa; Moniz-Pereira, José; Pimentel, Madalena (2011-06-01)."Functional analysis of the holin-like proteins of mycobacteriophage Ms6". Journal of Bacteriology 193 (11): 2793–2803. doi:10.1128/JB.01519-10. ISSN 1098-5530.PMC 3133122. PMID 21441511.

References

As of this edit, this article uses content from "1.E.18 The Lactococcus lactis Phage r1t Holin (r1t Holin) Family", which is licensed in a way that permits reuse under the Creative Commons Attribution-ShareAlike 3.0 Unported License, but not under the GFDL. All relevant terms must be followed.

Worked examples

Example 1 — a first encounter with Phage r1t holin family

Start with the simplest possible case. Write down what Phage r1t holin 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 Phage r1t holin 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 Phage r1t holin 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 Phage r1t holin family

In research: Phage r1t holin 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 Phage r1t holin 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: Phage r1t holin family is common in secondary-school and first-year university syllabi. It links to neighbouring topics Integral membrane proteins, Membrane proteins, Protein families, so understanding it makes those chapters shorter.
In everyday life: Look for Phage r1t holin 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 Phage r1t holin family in 20 minutes

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Frequently asked questions

What is Phage r1t holin family in simple terms?

Why does Phage r1t holin 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 Phage r1t holin 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 Phage r1t holin family.