Bulletin Spring‧Summer 1995

Dr. P. C. Shawgraduated from the Department of B i o l o g y of this u n i v e r s i t yand obtainedhis B.Sc. in f i r st classhonoursi n 1981 and M . P h i l . n 1983.He then pursued his d o c t o r a l studies at the Imperial College of Science and T e c h n o l o g y , U n i v e r s i t y of L o n d o n , on a Croucher F o u n d a t i o n scholarship. D r. Shawwasapostdoctoral f e l l owat the Imperial College before j o i n i nghisalmamater,the C U H K , asa lecturer in biochemistry in 1987. A Project to Overcome Existing Limitations In an attempt to overcome these limitations, a project was initiated by Dr. P. C. Shaw of the Department of Biochemistry. The aim was to try and find novel or rare restriction enzymes from bacterial strains in Hong Kong and its neighbouring regions. This research on restriction enzymes was supported initially by two direct grants from the Research Grants Council, and subsequently, by a contract grant from a biochemical company in the USA and a research grant from the Croucher Foundation. Until now, more than 100 restriction enzymes have been found in Dr. Shaw's laboratory. Some of these are unique or rare enzymes, or possess properties superior to previously known ones. The findings have been published in prestgious journals, including N u c l e i cA c i ds Research and Gene. Some of these strains, proudly carrying the designation HK for Hong Kong 一 for example, the B s i H K A I and the Ec/HKI — have made their way to commercial production by biochemical companies in the USA, with transfer fees and royalties accruing to the University. Hitherto Unknown Properties Discovered After these restriction enzymes were identified, they have been studied and some very interesting properties discovered. In a bacterial cell, for instance, methyltransferase coexists w i th restriction enzyme and the two of them form a restriction-modification system. Methyltransferase modifies the bacterial DNA to prevent the unwanted cleavage of its own restriction enzyme. In analysing the restriction-modification system of one of the clinically-isolated strain Escherichia coli HK31, Dr. Shaw's group has discovered an unusual methyltransferase M.EcoHK31I which requires two proteins instead of the usual one for functioning. Dr. Richard Roberts, the 1993 Nobel laureate inphysiology or medicine, has mentioned this discovery in the Federation of American Societies for Experimental Biology Summer Research Conference onRestriction Endonucleases and Methyltransferases held at Vermont, USA, in 1993, and has subsequently reported it in Volume 5 Issue 1of the NEB T r a n s c r i p t . The genes encoding the above restriction-modification system are now being further analysed. Research 25