Pii: S0166-6851(01)00402-9
نویسندگان
چکیده
The genes encoding the wild-type and six (five single and one double) mutant dihydrofolate reductase (DHFR) domains of the human malaria parasite, Plasmodium i ax (Pv), were cloned and expressed in Escherichia coli. The catalytic activities and the kinetic parameters of the purified recombinant wild-type and the mutant PvDHFRs were determined. Generally, all the PvDHFR mutants yielded enzymes with poorer catalytic activities when compared to the wild type enzyme. The widely used antifolates, pyrimethamine and cycloguanil, were effective inhibitors of the wild-type PvDHFR, but were 60 to 4000 times less active against the mutant enzymes. In contrast to the analogous S108N mutation of Plasmodium falciparum DHFR (PfDHFR), the single S117N mutation in PvDHFR conferred 4000and 1600-fold increased resistance to pyrimethamine and cycloguanil, respectively, compared to the wild-type PvDHFR. The S58R+S117N double mutant PvDHFR was 10to 25-fold less resistant than the S117N mutant to the inhibitors, but also exhibited higher kcat/Km value than the single mutant. The antifolate WR99210 was equally effective against both the wild-type and SP21 (S58R+S117N) mutant DHFRs, but was much less effective against some of the single mutants. Data on kinetic parameters and inhibitory constant suggest that the wild-type P. i ax is susceptible to antimalarial antifolates and that point mutations in the DHFR domain of P. i ax are responsible for antifolate resistance. © 2002 Elsevier Science B.V. All rights reserved.
منابع مشابه
Pii: S0166-6851(01)00261-4
Peroxisomes of higher eukaryotes, glycosomes of kinetoplastids, and glyoxysomes of plants are related microbody organelles that perform differing metabolic functions tailored to their cellular environments. The close evolutionary relationship of these organelles is most clearly evidenced by the conservation of proteins involved in matrix protein import and biogenesis. The glycosome can be viewe...
متن کاملPii: S0166-6851(01)00440-6
A simple and effective system has been developed from which a number of Plasmodium falciparum dihydrofolate reductase (pfDHFR) mutants conferring resistance to antifolates were randomly generated and characterized. The system exploited error-prone PCR to generate random mutations in the pfDHFR. Using the synthetic gene encoding for wild-type and quadruple mutant (N51I+C59R+S108N+I164L) pfDHFRs ...
متن کاملPii: S0166-6851(01)00388-7
A method has been developed for discovering patterns in DNA sequences. Loosely based on the well-known Lempel Ziv model for text compression, the model detects repeated sequences in DNA. The repeats can be forward or inverted, and they need not be exact. The method is particularly useful for detecting distantly related sequences, and for finding patterns in sequences of biased nucleotide compos...
متن کاملMAMCRA: a constrained-based multicast routing algorithm
Multicast routing algorithms that are capable of providing quality of service (QoS) to its members will play an important role in future communications networks. This paper discusses some fundamental properties of multicast routing subject to multiple QoS requirements. We will show that guaranteeing QoS and optimizing resource utilization are conflicting objectives and require a trade-off. We a...
متن کامل