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Peptide cyclization, a pivotal approach to modifying linear precursors of proteins and pepticles, has been used to enhance their biological activities and serum stabilities. Recently, sortase A (SrtA) from Staphyloccus aureus becomes a promising new technology for efficiently incorporating site specific modifications into proteins, conjugating the cell surface and cyclizing the linear peptides. In this study, we constructed two recombinant expression systems, one with chitin binding domain and the other with six-histidine tag and chitin binding domain on the N-terminal of SrtA, separately. The results of enzymatic kinetics indicate that the two recombinant tags do not impair the transpeptidase activity of SrtA compared with the standard reaction reported under the same reaction condition. The two synthesized peptides with N-ternimal three glycines and C-terminal penta-amino acid motif, LPETG, were cyclized using immobilized and recycled SrtA. The SrtA-based cyclization promises to represent a simple method for easy and efficient enzymatic synthesis of large cyclic peptides.
Aminoacyltransferases ; metabolism ; Bacterial Proteins ; metabolism ; Cyclization ; Cysteine Endopeptidases ; metabolism ; Enzymes, Immobilized ; metabolism ; Kinetics ; Peptides ; metabolism ; Peptides, Cyclic ; biosynthesis ; Staphylococcus aureus ; enzymology

7.Prenatal molecular diagnosis of four fetuses at high risk for X-linked adrenoleukodystrophy

Longfeng KE ; Zhihong WANG ; Huijuan HUANG ; Xiangdong TU ; Jian ZENG ; Bo LI ; Bosheng YANG ; Fenghua LAN

Chinese Journal of Obstetrics and Gynecology 2008;43(1):25-28

Objective To investigate methods for prenatal molecular diagnosis of fetuses at high risk for X-linked adrenoleukodystrophy(X-ALD).Methods The amniotic fluid was obtained and genomic DNA was isolated from amniotic fluid cells.Maternal contamination was evaluated by paternity test.PCRRFLP,sequencing and denaturing high performance liquid chromatography(DHPLC)were used to detect the ABCD1 gene of fetal genome.Results In the pedigree 1,the PCR product(799 bp)of the fetus 1 and her father(normal control)could be digested with BcnI. No P560L mutation,which was present in the index patient,was detected in the ABCD1 gene from the genomic DNA of the fetus 1 using direct sequencing.In the pedigree 2,the PCR product(232 bp)of the fetus 2 and her father could not be digested with MaeI and no Q177X mutation,which was present in the propositus,was detected in the ABCD1 gene from the genomic DNA of the fetus 2 using direct sequencing.In the pedigree 3,the PCR product(271 bp)was digested with AciI.the pattern of the fetus 3 and the propositus being the same,and the R617C mutation was found in the ABCD1 gene from the genomic DNA of the fetus 3 using direct sequencing.In the pedigree 4,the PCR product(269 bp)was analyzed with the DHPLC,and the pattern of elution peaks of the fetus 4 and her father was similar,but different from that of the propositus.No K276E mutation was detectable in the ABCD1 gene from the genomic DNA of the fetus 4 by using direct sequencing.Judging from the sex of the fetuses,fetuses 1 and 2 were normal homozygotes,fetus 3 was an ALD hemizygote,and fetus 4 was a normal hemizygote.Conclusion A new protocol for X-ALD prenatal molecular diagnosis is proposed,which would ensure the accuracy of prenatal diagnosis.