Biomedical subjects

Jun Liao

Publications and source records attributed to Jun Liao.

21 records · Page 2Linked to original sources

PubMed2002

Site-specific integration of the double-mutation glucose isomerase (GIG138PG247D) gene in Streptomyces lividans and its stable expression.

A recombinant expression plasmid pYH12, containing the double-mutation glucose isomerase (GIG138PG247D, GI2) coding gene and its natural regulatory sequence, was constructed for site-specific integration in Streptomyces. The resulting plasmid was introduced into Streptomyces lividans TK54 by protoplast transformation and two apramycin-resistance (AmR) transformants, designated GY2 and BY7, respectively, were obtained further based on enzyme assays. These results for polymerase chain reaction (PCR), Dot blot, and recovery of cloned fragments from the transformant chromosome indicated that the GI2 gene was integrated into the S. lividans chromosome by site-specific recombination, and which was further verified by Southern blot. We found that the free form of plasmid pYH12 co-existing with the integrated form was present in S. lividans. SDS-PAGE analysis showed that the GI2 gene was expressed in S. lividans. The intracellular GI2 specific activity was 1.15 U/mg. The stability of integrants demonstrated that the cloned GI2 gene was stably integrated and expressed even in the absence of selective pressure.

Aldose-Ketose Isomerases↗

PubMed2002

Three-dimensional structure of manganese superoxide dismutase from Bacillus halodenitrificans, a component of the so-called "green protein".

A so-called "green protein" has been purified from a moderate halophilic eubacterium, Bacillus halodenitrificans (ATCC 49067), under anaerobic conditions. The protein, which might play an important role in denitrification, dissociates mainly into two components after exposure to air: a manganese superoxide dismutase (GP-MnSOD) and a nucleoside diphosphate kinase. As a first step in elucidating the overall structure of the green protein and the role of each component, the 2.8-A resolution crystal structure of GP-MnSOD was determined. Compared with other manganese dismutases, GP-MnSOD shows two significant characteristics. The first is that the entrance to its substrate channel has an additional basic residue-Lys38. The second is that its surface is decorated with an excess of acidic over basic residues. All these structural features may be related to GP-MnSOD's high catalytic activity and its endurance against the special cytoplasm of B. halodenitrificans. The structure of GP-MnSOD provides the basis for recognizing its possible role and assembly state in the green protein.

Amino Acid Sequence↗

PubMedDate not supplied

Active learning with support vector machines in the drug discovery process.

We investigate the following data mining problem from computer-aided drug design: From a large collection of compounds, find those that bind to a target molecule in as few iterations of biochemical testing as possible. In each iteration a comparatively small batch of compounds is screened for binding activity toward this target. We employed the so-called "active learning paradigm" from Machine Learning for selecting the successive batches. Our main selection strategy is based on the maximum margin hyperplane-generated by "Support Vector Machines". This hyperplane separates the current set of active from the inactive compounds and has the largest possible distance from any labeled compound. We perform a thorough comparative study of various other selection strategies on data sets provided by DuPont Pharmaceuticals and show that the strategies based on the maximum margin hyperplane clearly outperform the simpler ones.

Computer-Aided Design↗