Because nucleic acids are sensitive to their activity, some enzymes with a broad action (such as phosphodiesterases, which hydrolyse phosphoric acid esters) are referred to as nucleases. Animals and plants both have nucleases.
Restriction enzymes are nucleases that only split DNA molecules in which specific subunits are recognised. Some split the target DNA molecule at random locations (Type I), while others split it solely at the recognition site (Type II) or at a predetermined distance from the recognition site (Type III) (Type III). Restriction enzymes of type II and III are useful for deciphering the sequence of bases in DNA molecules. They are crucial in the field of recombinant DNA technology, also known as genetic engineering.
Nucleases are a varied group of enzymes that hydrolyze DNA and RNA’s phosphodiester bonds. They play important roles in genetic quality control in nature, including as DNA proofreading, base, nucleotide, mismatch, and double-strand repairs, homologous recombination, and turnover. Nucleases are also widely used in molecular and cell biology applications that need precision nucleic acid manipulation, such as restriction digestion, nucleic acid degradation, and trimming. Nucleases are categorised into different categories based on their functions and selectivity for different types of nucleic acid substrates.
Nuclease Types:
- Endonucleases: Endonucleases cut DNA and RNA from the middle of the chain, with various degrees of recognition of the sites. Restriction endonucleases, often known as restriction enzymes, are sequence specific cloning and gene analysis tools. DNase I and Benzonase, for example, are indiscriminate and are employed to completely digest DNA or RNA samples.
- Exonucleases: Exonucleases, unlike endonucleases, cleave nucleotides from the 3′ or 5′ ends of DNA and RNA chains one at a time. Exonucleases are used to selectively degrade single-stranded DNA while also removing overhangs.
- DNases: DNases, or deoxyribonucleases, digest DNA rather than RNA, and different varieties can cut from the inside or from the ends. DNase I is frequently used in research to remove contaminating DNA from RNA and protein samples, clean cell cultures, and perform DNA fragmentation experiments.
- RNases: Ribonucleases, on the other hand, prefer to digest RNA than DNA. RNases (usually known as RNase A and RNase H) are frequently employed to remove contaminated RNA from samples and RNA tests. RNases are often more selective for single-stranded RNA than hybridised RNA (with the exception of RNase H).
- Strand-specific Nucleases: Because of their selectivity for single-stranded or double-stranded nucleic acids, a number of nucleases have been developed. Micrococcal nuclease, S1 nuclease, and Mung Bean nuclease are utilised for selective digestion and removal of overhangs in single-stranded DNA and RNA (including DNA-RNA hybridizations). Duplex-specific nucleases, on the other hand, prefer double-stranded DNA or RNA to single-stranded DNA or RNA.
- Other nucleases: Cas9 (streptococcus pyogenes associated protein 9) is a nuclease generated from Streptococcus pyogenes that is utilised in the CRISPR/Cas9 genome editing technology. Cas9 nuclease can be used to modify, insert, or delete a specific section of the genome when combined with a sequence-specific guide RNA.
Virulence factor
The pathogenicity of pathogenic organisms varies greatly. A strain of bacteria, for example, may be more virulent than other strains of the same species. The so-called virulence factors are frequently linked to a pathogen’s pathogenicity. A virulence factor is a protein that allows an organism to infiltrate and cause disease in its host. It also evaluates how much damage has been done to the host. These substances could be secretory, membrane-associated, or cytosolic.
The ability of microorganisms to reproduce within their host cells is an example of a virulence factor. These characteristics are critical to epidemiology in microbiology, especially when tracking a novel pathogenic strain. This is because the strain is frequently very virulent, making it more harmful, if not fatal, to its host. The method of entry into the host, the pathobiological machinery used, and the consequences on the host’s immune response are some of the virulence factors studied by researchers. For example, viral virulence factors are proteins that the infective virus induces to be generated by the host’s own protein machinery.
Bacterial virulence factors are proteins that are encoded by their own genes or plasmids acquired through horizontal gene transfer. The harm may be exacerbated by the host’s overly reactive immune response, which occurs when immune cells are so stimulated by the presence of certain virulence factors that they damage host cells in an attempt to fight the infection. As a result, these virulence factors are one of the primary targets in medical research aimed at developing new therapies and vaccines.
Example
A virulent virus is the human immunodeficiency virus, or HIV. It is the virus that causes AIDS. It is virulent because it uses techniques to avoid being detected by the host’s immune cells. It infects the T-helper cell, which is one of the immunological cells. As a result, the host’s immunological response has already been weakened and degraded.
The lyssavirus, which causes rabies, is another example. It enters muscle cells and hijacks them, then travels to the nervous system via neuromuscular junctions. As a result, it is classified as neurovirulent, or capable of causing disease in the neurological system.
Two human pathogens, Mycobacterium tuberculosis (cause of tuberculosis) and Bacillus anthracis, are examples of bacteria (causative agent of anthrax).
Conclusion
Nucleases are enzymes that are specifically designed to break down the nucleotides that make up DNA and RNA. Adenine, thymine, guanine, and cytosine make up nucleotides in DNA, while uracil replaces thymine in RNA. Nucleases are introduced and cleave these nucleotides apart.