9600971 Perona Recent discoveries of new catalytic functions of RNA have greatly heightened awareness of the pivotal role of this molecule in living organisms. A full appreciation of the biological function of RNA must include a thorough description of how its three-dimensional structure is organized, but to date very few atomic-level descriptions of RNA molecules are available. Our previous work on crystallization and structure determination of the glutaminyl-tRNA synthetase-tRNAGIn complex provides a unique vehicle to rapidly determine the structures of new domains of RNA, the focus of the proposed project. The pre-existing crystal lattice of this large protein-RNA complex will be exploited by inserting new domains of RNA into specific positions of the tRNA, so that the new material is accomodated in the solvent interstices of the crystal. In-vitro selection methods are employed to obtain novel hybrid RNA molecules which fold correctly and retain biological activity. These new RNAs are chosen for their potential to teach us the underlying rules of three-dimensional folding and for their present-day biological significance. A rapid increase in new RNA structures will provide fundamental insight into RNA-based cellular processes and may have further implications to defining a new class of targets for structure-based drug design. The establishment of a laboratory engaged in Macromolecular Crystallography has been a long-awaited development at UCSB. Consequently, a significant activity in the next five years will be the education of students as well as other faculty members in related fields. Because a joint appointment is held in Chemistry and in an Interdepartmental Biochemistry and Molecular Biology Program (BMB), the range of interactions will be especially broad. A new graduate course in crystallography will be developed, and an existing course in Physical Biochemistry has already been extensively revised. State of the art data collection and computer graphics facilities enhance the educat ional opportunities by providing hands-on experience in the most important techniques. The arrival of crystallography also marks the onset of a long-term growth phase in Biochemistry and Biophysics at UCSB. Thus, there will be substantial participation in several new undergraduate curricula related to Structural Biology: a new B.S. degree in Biochemistry to be awarded by the Chemistry department, and an interdisciplinary program in Pharmacological Sciences. The University also possesses strong commitments to supporting undergraduate research opportunities, as manifested by programs funded by the Howard Hughes Medical Institute and the Materials Research Laboratory. Direct mentoring of undergraduates in the laboratory will be an important aspect of the educational program. Collaborative projects inside the University, as well as with senior scientists at other institutions, enhance the educational opportunities for students in the laboratory. %%% The fundamental building-block molecules in all living cells are DNA, RNA and protein. DNA encodes the genetic information within its nucleotide sequence, but for the cell to function this information must first be copied into a similar molecule, RNA, and then translated into protein. Until recently it was thought that proteins were the only molecules in cells capable of carrying out the necessary chemical and mechanical life processes. However, new discoveries have shown that RNA has a similar capability. We seek to understand how RNA can perform complex functions historically attributed only to protein. To do this requires visualization of RNA structure in three dimensions, a feat accomplished by inducing very pure samples of RNA to form well-ordered crystals which are analyzed by Xray diffraction. In our laboratory we are developing a new experimental system to grow crystals of RNA molecules bound to protein rather than in the usual unbound state. This system has the potential to allow us to rapidly determine many new RNA structures. We expect that the structures will provide us with fundamental insight into the functional roles of RNA in essential cellular processes. ***