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Holin
Holins are a diverse group of small proteins produced by dsDNA bacteriophages in order to trigger and control the degradation of the host's cell wall at the end of the lytic cycle. Holins form pores in the host's cell membrane, allowing lysins to reach and degrade peptidoglycan, a component of bacterial cell walls. Holins have been shown to regulate the timing of lysis with great precision. Over 50 unrelated gene families encode holins, making them the most diverse group of proteins with common function. Together with lysins, holins are being studied for their potential use as antibacterial agents. While canonical holins act by forming large pores, pinholins such as the S protein of lambdoid phage 21 act by forming heptameric channels that depolarize the bacterial membrane. They are associated with SAR endolysins, which remain inactive in the periplasm prior to the depolarization of the membrane. Viruses that infect eukaryotic cells may use similar channel-forming proteins call ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
T4 Holin
The T4 Holin FamilyTC# 1.E.8 is a group of putative pore-forming proteins that does not belong to one of the seven holin superfamilies. T-even phage such as T4 use a holin-endolysin system for host Lysis, cell lysis. Although the endolysin of Bacteriophage, phage T4 encoded by the e gene (Lysozyme E) was identified in 1961, the holin (product of gene t and called T-holin) was not characterized until 2001. A representative list of proteins belonging to the T4 holin family can be found in thTransporter Classification Database Structure T4 holin is fairly large, about 218 amino acyl residues (aas) in length. The protein is highly hydrophilic with 49 acidic and basic residues distributed along its length and a single putative transmembrane segment (TMS) near its N-terminus, leaving most of the protein in the periplasm. Function The large periplasmic domain is a major determinant in the timing mechanism and is involved in lysis inhibition (LIN). LIN involves the antiholin rI protein ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CidA/LrgA Holin
The CidA/LrgA Holin (CidA/LrgA Holin) FamilyTC# 1.E.14 is a group of proteins named after CidATC# 1.E.14.1.2 and LrgATC# 1.E.14.1.1 of ''Staphylococcus aureus.'' CidA ''and'' LrgA are homologous holin and anti-holin proteins, each with 4 putative transmembrane segments (TMSs). Members of the CidA/LrgA holin family also include putative murine hydrolase exporters from a wide range of Gram-positive and Gram-negative bacteria as well as archaea. Most CidA/LrgA holin family proteins vary in size between 100 and 160 amino acyl residues (aas) in length although a few are larger. Function It has been proposed that CidA and CidB (23% and 32% identical to LrgA and LrgB, respectively) are involved in programmed cell death in a process that is analogous to apoptosis in eukaryotes. These proteins are known to regulate and influence biofilm formation by releasing DNA from lysed cells which contributes to the biofilm matrix. CidA, a 131 aa protein with 4 putative TMSs, is believed to be the h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
BlyA Holin Family
The BlyA Holin FamilyTC# 1.E.17 is a group of holin proteins that are approximately 55-70 amino acyl residues (aas) in length and exhibit one transmembrane segment (TMS). A representative list of the proteins belonging to the BlyA holin family can be found in thTransporter Classification Database BlyAB The BlyA membrane protein and the BlyB soluble accessory protein are encoded on the conserved cp32 plasmid of ''Borrelia burgdorferi,'' which can be packaged into a bacteriophage particle. These two proteins had previously been proposed to comprise a hemolysis system, but Damman et al. (2000) provided evidence that BlyAB functions as a prophage-encoded holin system. BlyA promotes endolysin-dependent lysis of an induced lambda lysogen that is defective for the lambda holin S gene. The holin pores are generally stable and nonspecific, allowing endolysin access to the peptidoglycan. Introduction of the ''Borrelia burgdorferi'' ''blyAB'' locus into ''Escherichia coli ''Escheric ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Holin Superfamily III
The Holin Superfamily III is a superfamily of integral membrane transport proteins. It is one of the seven different holin superfamilies in total. In general, these proteins are thought to play a role in regulated cell death, although functionality varies between families and individual members. Members of the holin superfamily III are derived from Pseudomonadota, Synergistota, Actinomycetota, Deinococcota, and Archaea. This superfamily includes seven TC families: 1.E.2- The λ Holin S (λ Holin) Family 1.E.3- The P2 Holin (P2 Holin) Family 1.E.4- The LydA Holin (LydA Holin) Family 1.E.5- The PRD1 Phage P35 Holin (P35 Holin) Family 1.E.20- The ''Pseudomonas aeruginosa'' Hol Holin (Hol Holin) Family 1.E.34- The Putative Actinobacterial Holin-X (Hol-X) Family 1.E.41- The Deinococcus/Thermus Holin (D/T-Hol) Family Members of all families (with the exception of the Hol-X familyTC# 1.E.34 appear to have three transmembrane segments (TMSs). Members of the Hol-X family appear to h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Holin Superfamily II
The Holin superfamily II is a superfamily of putative pore-forming proteins. It is one of the seven different holin superfamilies in total. In general, these proteins are thought to play a role in regulated cell death, although functionality varies between families and individual members. The Holin superfamily II includes the TC families: 1.E.1- The P21 Holin S (P21 Holin) Family 1.E.6- The T7 Holin (T7 Holin) Family 1.E.7- The HP1 Holin (HP1 Holin) Family 1.E.25- The ''Pseudomonas'' phage F116 Holin (F116 Holin) Family 1.E.50- The Beta-Proteobacterial Holin (BP-Hol) Family All four of these families are derived from Pseudomonadota and are of relatively small sizes, the average size of the proteins within the entire superfamily is 78 ± 14 amino acyl residues (aas). Some exceptions can be found (i.e., Lysis S family protein with 720 aasTC# 1.E.1.1.7. As in holin superfamily I, proteins in these families generally exhibit of 2 transmembrane spanners (TMSs). Families 1 and 6 in Su ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lytic Cycle
The lytic cycle ( ) is one of the two cycles of viral reproduction (referring to bacterial viruses or bacteriophages), the other being the lysogenic cycle. The lytic cycle results in the destruction of the infected cell and its membrane. Bacteriophages that only use the lytic cycle are called virulent phages (in contrast to temperate phages). In the lytic cycle, the viral DNA exists as a separate free floating molecule within the bacterial cell, and replicates separately from the host bacterial DNA, whereas in the lysogenic cycle, the viral DNA is located within the host DNA. This is the key difference between the lytic and lysogenic (bacterio)phage cycles. However, in both cases the virus/phage replicates using the host DNA machinery. Description The lytic cycle, which is also commonly referred to as the "reproductive cycle" of the bacteriophage, is a six-stage cycle. The six stages are: attachment, penetration, transcription, biosynthesis, maturation, and lysis. # Attachme ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Holin Superfamily IV
The Holin superfamily IV is a superfamily of integral membrane transport proteins. It is one of the seven different holin superfamilies in total. The Holin superfamily IV includes the TC families: 1.E.10- The ''Bacillus subtilis'' φ29 Holin (φ29 Holin) Family 1.E.16- The Cph1 Holin (Cph1 Holin) Family 1.E.19- The ''Clostridium difficile'' TcdE Holin (TcdE Holin) Family 1.E.40- The Mycobacterial 4 TMS Phage Holin (MP4 Holin) Family Superfamily IV includes four TC families, which includes members from ''Bacillota'', ''Actinomycetota'' and '' Fusobacteriota''. Their average sizes are (in amino acyl residues (aas)): TC# 1.E.10 - 138 ± 6 aas TC# 1.E.16 - 149 ± 15 aas TC# 1.E.19 - 141 ± 12 aas TC# 1.E.40 - 173 ± 149 aas Thus, there is very little size variation among family members, except for family 40, which has members larger than the other proteins in this superfamily. All members of families 10 and 19 and many members of family 16 appear to have 3 transmembrane segment ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Holin Superfamily I
The Holin Superfamily I (aka the CDD phage holin1 superfamily) is a superfamily of integral membrane transport proteins. It is one of the seven different holin superfamilies in total. In general, these proteins are thought to play a role in regulated cell death, although functionality varies between families and individual members. Its main constituent is the Phi11 Holin (φ11 Holin) Family. This family is made up of over 270 putative pore-forming proteins, all from '' Bacillota''. On average, proteins belonging to the holin I superfamily are about 100 amino acyl residues (aas) in length, although a large size variation exists among proteins of this superfamily. There does not seem to be deviation from the standard two transmembrane segments that these proteins possess. See also * Holins * Lysin Lysins, also known as endolysins or murein hydrolases, are hydrolytic enzymes produced by bacteriophages in order to cleave the host's cell wall during the final stage of the lytic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bacillus Spore Morphogenesis And Germination Holin Family
The ''Bacillus'' Spore Morphogenesis and Germination Holin (BSH) FamilyTC# 1.E.23 is a family of proteins named after a holin in ''Bacillus subtilis'' described to be involved in spore morphogenesis and germination by Real et al (2005). The gene encoding this holin is ''ywcE.'' Mutants lacking this gene or its product have spores that exhibit outer coat defects. These spores lack the characteristic striatal pattern resulting in the failure of the outer coat to attach to the underlying inner coat. Finally, the mutant spores accumulate reduced amounts of dipicolinic acid. BSH proteins average about 90 amino acyl residues in length and exhibit 3 transmembrane segments (TMSs). A representative list of homologous proteins, found only in ''Bacillus'' species, is available in thTransporter Classification Database See also * Holin Holins are a diverse group of small proteins produced by dsDNA bacteriophages in order to trigger and control the degradation of the host's cell wall at the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lysins
Lysins, also known as endolysins or murein hydrolases, are hydrolytic enzymes produced by bacteriophages in order to cleave the host's cell wall during the final stage of the lytic cycle. Lysins are highly evolved enzymes that are able to target one of the five bonds in peptidoglycan (murein), the main component of bacterial cell walls, which allows the release of progeny virions from the lysed cell. Cell-wall-containing Archaea are also lysed by specialized pseudomurein-cleaving lysins, while most archaeal viruses employ alternative mechanisms. Similarly, not all bacteriophages synthesize lysins: some small single-stranded DNA and RNA phages produce membrane proteins that activate the host's autolytic mechanisms such as autolysins. Lysins are being used as antibacterial agents due to their high effectiveness and specificity in comparison with antibiotics, which are susceptible to bacterial resistance. Structure Double-stranded DNA phage lysins tend to lie within the 25 to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
PhiU53 Holin Family
The ''Firmicute'' Phage φU53 Holin (φU53 Holin) Family (TC# 1.E.13) consists of putative holins that range in size from 117 to 124 amino acyl residues (aas) in length and exhibit 3 transmembrane segments (TMSs) found in Bacillota phage. While annotated as holins, it appears as though many members of the φU53 holin family are not yet functionally characterized. A representative list of homologues can be found in the Transporter Classification Database. See also * Holin * Lysin Lysins, also known as endolysins or murein hydrolases, are hydrolytic enzymes produced by bacteriophages in order to cleave the host's cell wall during the final stage of the lytic cycle. Lysins are highly evolved enzymes that are able to target ... * Transporter Classification Database Further reading * Chandry, P. S.; Moore, S. C.; Boyce, J. D.; Davidson, B. E.; Hillier, A. J. (1997-10-01)"Analysis of the DNA sequence, gene expression, origin of replication and modular structure of the Lactococcu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
NP-holin Family
The ''Neisserial'' Phage-associated Holin (NP-Holin) FamilyTC# 1.E.22 is a family of small proteins, between 47–53 amino acyl residues in length, that exhibit a single N-terminal transmembrane segment (TMS). Although annotated as phage proteins or holins, NP-Holin proteins are not yet functionally characterized, thus more research is needed to confirm holin activity. A representative list of proteins belonging to the NP-Holin family can be found in thTransporter Classification Database See also * Holin * Lysin Lysins, also known as endolysins or murein hydrolases, are hydrolytic enzymes produced by bacteriophages in order to cleave the host's cell wall during the final stage of the lytic cycle. Lysins are highly evolved enzymes that are able to target ... * Transporter Classification Database Further reading * References {{CCBYSASource, sourcepath=http://tcdb.org/search/result.php?tc=1.E.22, sourcearticle=1.E.22. The Neisserial Phage-associated Holin (NP-Holin) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |