ABSTRACT
Petite integration frequency 1 (PIF1) helicases are ubiquitous enzymes which play vital roles in nearly all DNA metabolic processes. In recent years, the biochemical activity and three-dimensional structure of several PIF1 helicases have been reported, but there are few reports on the PIF1 helicase of bacteria living in extreme environments. In this paper, a series of biochemical and biophysical techniques were used to study the Thermodesulfovibrio yellowstonii PIF1 (Ty.PIF1) helicase in many aspects. Ty. PIF1 was obtained with a purity of over 90% and good uniformity using the prokaryotic expression and purification system. Ty.PIF1 is a monomer with a calculated molecular weight of 60 kD in solution. Ty. PIF1 has high thermal stability. The secondary structure remains stable when the temperature is below 65 ℃, and the secondary structure changes only when the temperature is above 70 ℃. The optimal unwinding temperature of Ty.PIF1 in vitro is 45 ℃, which is not the optimal temperature for the survival of thermodesulfovibrio yellowstonii. It indicates that when Ty.PIF1 exerts its enzymatic activity in vivo, it may require the participation of other cofactors. Ty.PIF1 can exert unwinding activity in a wide temperature range (20-55 ℃), and the presence of enzyme activity at 55 ℃ indicates that Ty.PIF1 has heat-resistant properties. Ty.PIF1 prefers to bind to substrates containing ssDNA, but there is certain requirement for the length of the ssDNA, which is at least 4 nt in length. Ty.PIF1 can also bind to the G
ABSTRACT
Objective To detect genetic polymorphism of myeloperoxidase (MPO) gene and catalase (CAT) gene and their activities, and to analyze their relationship with arsenic poisoning caused by coal-burning. Methods One hundred and thirty arsenic poisoning patients were chosen as case group in Jiaole Village, Xingren County, Guizhou Province(an endemic area). One hundred and forty healthy residents living in 13 km away were chosen as control group. Their blood was collected. Polymerase chain reaction-restriction fragment length polymorphism technique(PCR-RFLP) was used to detect polymorphism of MPO-463G/A and CAT-262C/T. Ultraviolet spectmphotometer method was used to detect myeloperoxidase activity. Chromatometry method was used to detect catalase activity. Results The genotype frequency of MPO-463G/A at GG, GA, AA site was 47.24%(60/127), 44.09%(56/127),8.67% (11/127) in case group and 42.34% (58/137),48.17% (66/137)1,9.49% (13/137) in control group, respectively. The difference between the two groups was not significant(χ2 = 0.642, P > 0.05). The genotype frequency of CAT-262C/T, at CC, CT, TT site was 65.60%(82/125),28.80%(36/125),5.60%(7/125) in case group and 76.51%(101/132), 18.94% (25/132) ,4.55% (6/132) in control group, respectively, without significant difference (χ2 =3.845, P>0.05). The relationship between polymorphism of MPO-463G/A and CAT-262C/T and the risk of arsenic poisoning was not found in this study(ORadj= 1.36, 95%CI: 0.74-2.50 for MPO; ORadj=1.35, 95%CI: 0.69-2.63 for CAT). The activities of MPO and CAT were (25.30±8.70)U/L and (2.80± 1.09)×103 U/L in case group, while (22.76±7.59)U/L and (3.90±1.01)×103U/L in control group with a significant difference(F=0.760 for MPO, F=0.855 for CAT, all P < 0.05). The genotype of MPO-463G/A and CAT-262C/T was not found to have relationship with the activities of MPO, CAT(F=1.312,2.822 for MPO; F= 0.151,0.036 for CAT, P>0.05). Conclusions Genetic polymorphism of MPO-463G/A and CAT-262C/T is not found to have relationship with arsenic poisoning. Arsenic can lead to the change of MPO and CAT activity, which, however, may not be affected by MPO-463G/A and CAT-262C/T polymorphism.