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Holins
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 calle ... [...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 cell lysis. Although the endolysin of 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 of T4 (SeTC# 1.E.8.1 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ArpQ Holin Family
The ArpQ Holin (ArpQ Holin) FamilyTC# 1.E.15 consists of a single holin-like protein 58 amino acyl residues (aas) in length with 2 transmembrane segments (TMSs). This protein is encoded by the ''arpQ'' gene in ''Enterococcus hirae''. While annotated as a holin, it is not functionally characterized. 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 targ ... * Transporter Classification Database References Further reading * * {{CCBYSASource, sourcepath=http://tcdb.org/search/result.php?tc=1.E.35, sourcearticle=The Mycobacterial 1 TMS Phage Holin (M1 Hol) Family, revision=699838558 Protein families Membrane proteins Transmembrane proteins Transmembrane transporters Transport proteins Integral membrane proteins Holins ... [...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 targ ... * 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] |
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 * Lysin Lysins, also known as endolysins or murein hydrolases, are hydrolytic enzymes produced by bacteriophages in order to cleave the host's cell wall ... [...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 targ ... * 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] |
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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dp-1 Holin Family
The Bacterophase Dp-1 Holin (Dp-1 Holin) FamilyTC# 1.E.24 is a family of proteins present in several Gram-positive bacteria (i.e., ''Enterococcus faecalis)'' and their phage. The genes coding for the lytic system of the pneumococcal phage, Dp-1, has been cloned and characterized. The holin of phage Dp-1 is 74 amino acyl residues (aas) long with two putative transmembrane segments (TMSs) (residues 12-32 and 39-57). The lytic enzyme of Dp-1 (Pal), an N-acetyl-muramoyl-L-alanine amidase, shows a modular organization similar to that described for the lytic enzymes of ''Streptococcus pneumoniae'' and its bacteriophage in which change in the order of the functional domains changes the enzyme specificity. A representative list of proteins belonging to the Dp-1 family 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' ... [...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 i ... [...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 VII
The Holin superfamily VII 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. The Holin superfamily VII includes one TC family: 1.E.36- The Mycobacterial 2 TMS Phage Holin (M2 Hol) Family Superfamily VII consists of familTC# 1.E.36 which has six subfamilies, all distantly related to each other. Reddy and Saier (2013) found that there was also some indication that this family could possibly be related to the SPP1 Holin familyTC# 1.E.31 and the 2/3 Holin familyTC# 1.E.33. These three families share the characteristics that they consist of members that are of about the same sizes and have 2 transmembrane segments (TMSs). There is however an exception; subfamily 6TC# 1.E.36.6 includes proteins displaying 4 putative TMSs. See also * Holin * Lysin Lysins, also known ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Holin Superfamily VI
The Holin superfamily VI 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. The Holin superfamily VI includes two TC families: 1.E.12The φAdh Holin (φAdh Holin) Family1.E.26- The Holin LLH (Holin LLH) Family Superfamily VI includes families with members only from ''Bacillota''. These proteins appear to have one N-terminal transmembrane segment (TMS), followed by an amphipathic, weakly hydrophobic peak that was not predicted to be transmembrane by the topological programs used by Reddy and Saier (2013). The average sizes of the members of the two families belonging to the Holin superfamily VI are 135 ± 11 and 130 ± 26 amino acyl residues (aas), respectively. See also * Holin * Lysin Lysins, also known as endolysins or murein hydrolases, are hydrolytic enz ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Holin Superfamily V
The Holin superfamily V 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. The Holin superfamily V includes the TC families: 1.E.21- The Listeria Phage A118 Holin (Hol118) Family 1.E.29- The Holin Hol44 (Hol44) Family Superfamily V includes protein families classified in the Transporter Classification Database aTC# 1.E.21anTC# 1.E.29 Both families possess members from ''Bacillota'', ''Actinomycetota'' and ''Chloroflexota''. Proteins of this superfamily all appear to have 3 transmembrane segments (TMSs) and have average sizes of 97 and 101 amino acyl residues (aas), respectively. 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |