S-A5-02 De novo design of helical proteins

Symposia Lectures S-A542 DE NOVO DESIGN OF HELICAL PROTEINS DE GRADO. W.F. University of Pennsylvania,Dept. of Biochemistry & Biophysics,Philadelphia (USA)

S-A-3 DESIGN AND ENGINEERING OF MODULE.SUBSTITUTED HEMOPROTEINS BASED ON THE EXON-SHUFFLING HYPOTHESIS MORISHIMA LWAKASUGI K, INABA K, ISHIMORI K.

Our group has recently adopted a synthetic approach to understanding the structural basis for protein function. In order to test some of the rules and concepts that are believed to be important for protein folding and stability, we are attempting to design some simple proteins that should fold into three-dimensional predetermined structures. Several types of helical proteins have been designed including two-stranded coiled coils, three-stranded coiled coils, and four-helix bundle proteins. The design and structure determination of these model proteins have led to a deepened understanding of the interplay of forces in determining the unique folded conformations of proteins -hydrophobic interactions are important for driving the folding in aqueous environment, but this force al::e leads to structures globular with fluctuating structures. To achieve a uniquely folded structure requires consideration of specific van der Waals packing, hydrogen bonding, and ion-ligand interactions.

Devnt of Molecular Untveaity(Japan)

Kyoto

Purpose:Detailed structural analysis of proteins have revealed that some proteins structures are constructedby “modules”, which are compact structural units and correspond to exons on gene structure.To gain an insight into structural and functional significance of the module in hemoproteins, we have prepared several modulesubstituted hemoproteins by exon-shuffling among myoglobin, hemoglobin a- and @subunits and cytochrome bg. Methods and Resulta:We present here some results from structural and functional examinations of module-substitutedglobins, in which one or two modules are replaced by the corresponding modules of other globins. For example, the module-substituted P-subunit or Mb having the module M4 from the a-subunit assembledwith the B-subunit, indicating that the module M4 plays a crucial role in the specific subunit associationin globins. Conclusions: The module substitution is a potential method to design and produce novel functional proteins.

S-Bl-01 NUCLEIC ACID STRUCTURE RECOGNITION

Engineering,

S-Bl-02 DNA TOP MEC&&+NI&i’i~ RECENT STRUCTURAL AND BIOCHEMICAL STUDIES WANG JC Department of Molecular and Cellular Biology, Harvard University

AND

Purpose: To establish enwal foldin principles for branched nucleic au‘&,andthero&in recognition and generation of catalysis.

There are three distinct subfamilies of DNA topoisomerases, two type I subfamilies that transport one DNA strand through a transient break in aaother. and one type II subfamily that couples ATP binding and hydrolysis to the transport of one duplex DNA through another. All three subfamilies of topoisomerases are present in eukaryotic cells. Recent structural and biochemical studies are beginning to provide molecular sketches on how these cnxymes manipulate DNA. This presentltion focuses on the coupling of ATP usage to DNA transport by eukaryotic DNA topoisomerase Ii. A single DNA-bound dimeric enzyme admits a second double-stranded DNA through one set of opan jaws at its N-terminal ends. Binding of ATP than closes this N-terminal protein gate and forces the admitted DNA through an enzyme-mediated gate in the other enzyme-bound DNA segment and expels It t&u& a saeond sat of jaws close to the C-termini of the enyme poiypeptides. 6