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Biochemistry
Published in Ronald Fayer, Lihua Xiao, Cryptosporidium and Cryptosporidiosis, 2007
Cryptosporidium possesses two distinct types of replication protein A large subunits (RPA1), one of which belongs to the short-type proteins only found in unicellular organisms (Zhu et al., 1999; Millership and Zhu, 2002). All three RPA subunits (i.e., RPA1 to 3) have been identified from the genome, and some of their biochemical features, including DNA-binding kinetics and dissociation constants, have been studied in detail (Millership et al., 2004a; Rider et al., 2005). RPA is actually a single-stranded DNA (ssDNA)-binding protein (SBP) involved in DNA replication, repair, and recombination. The presence of unique RPA species in Cryptosporidium [and other apicomplexans or some distant protists such as the trypanosomatid Crithidia fasciculate (Brown et al., 1994; Voss et al., 2002)] implies a possible significant difference between apicomplexans and higher eukaryotes in regulating DNA replication, repair, or recombination.
Detection of respiration changes inside biofilms with microelectrodes during exposure to antibiotics
Published in Journal of Environmental Science and Health, Part A, 2019
Jun Lin, Zechen Wang, Yue Zang, Dong Zhang, Qing Xin
Since the discovery of penicillin, research concerning the action mechanism of antibiotics has never ceased. Accordingly, antibiotics are classified into two categories: bactericidal drugs, which kill cells with an efficiency over 99.9%, and bacteriostatic drugs, which stop bacteria from reproducing.[1] For both classes, cellular damage is considered to be achieved via drug–target interactions, which predominantly involve inhibition of either DNA replication, protein synthesis or cell-wall turnover.[2] Recent studies have suggested that antibiotics also induce metabolic alteration as a secondary response to their target interaction.[3,4] They found that the response of planktonic cells to bactericidal agents involves accelerated respiration, whereas the response to bacteriostatic agents involves suppressed cellular respiration. Furthermore, evidence suggested that the rates of respiration for free cells were linked to the efficacy of bactericidal antibiotics.[5,6] Thus, monitoring the metabolic alteration can be an effective way to estimate the influence of antibiotics on cells.
Recombinant expression and characterization of yeast Mrc1, a DNA replication checkpoint mediator
Published in Preparative Biochemistry & Biotechnology, 2020
For the continuation of species, it is important to preserve genetic information and pass it on to future generations without errors. This process relies on a complete and reliable DNA replication process. If the DNA replication process becomes unstable or out of control, the correct delivery and expression of various types of genetic information cannot be guaranteed, resulting in various defects of the organism and various diseases including cancer, and even death. In order to cope with these risks, the organism is equipped with a corresponding DNA replication checkpoint mechanism and a repair mechanism.[1] In Saccharomyces cerevisiae (S. cerevisiae), Mec1 (serine/threonine-protein kinase (ATR) in human) is a phosphatidylinositol 3-kinase-like protein kinase (PIKK), which plays a central role in DNA replication checkpoint pathway. Ddc2 (ATR Interacting Protein (ATRIP in human)) acts as a regulatory subunit of Mec1 and forms protein complexes with Mec1.[2–4] The Mec1-Ddc2 complex is recruited to the stalled replication fork by replication protein A (RPA)-single stranded DNA (ssDNA). Ddc1, Mec3, and Rad17 are the other three proteins required for replication checkpoints, which form a trimer complex whose structure is thought to be similar to the proliferating cell nuclear antigen (PCNA).[5–10] The homolog of this trimer in human is Rad9-Hus1-Rad1 (9-1-1 complex). Current study found that the activation of Mec1/Ddc2 in S. cerevisiae is regulated by the 911 complex, and this control is dependent on cell cycle progression. Another necessary protein for replication checkpoint is Rad24 (Rad17 in human), which is similar to an RFC subunit and binds to RFCs2-5 to form a complex.[11] The Rad24-RFC complex loads the Mec3-Rad17-Ddc1 complex into the location where DNA is damaged or replication is blocked, and acts as a sensor to participate in the checkpoint response.