Cold Adaptation of a Mesophilic Subtilisin-like Protease by Laboratory Evolution

Enzymes isolated from organisms native to cold environments generally exhibit higher catalytic efficiency at low temperatures and greater thermosensitivity than their mesophilic counterparts. In an effort to understand the evolutionary process and the molecular basis of cold adaptation, we have used directed evolution to convert a mesophilic subtilisin-like protease from Bacillus sphaericus, SSII, into its psychrophilic counterpart. A single round of random mutagenesis followed by recombination of improved variants yielded a mutant, P3C9, with a catalytic rate constant (kcat) at 10 °C 6.6 times and a catalytic efficiency (kcat/KM) 9.6 times that of wild type. Its half-life at 70 °C is 3.3 times less than wild type. Although there is a trend toward decreasing stability during the progression from mesophile to psychrophile, there is not a strict correlation between decreasing stability and increasing low temperature activity. A first generation mutant with a >2-fold increase in kcat is actually more stable than wild type. This suggests that the ultimate decrease in stability may be due to random drift rather than a physical incompatibility between low temperature activity and high temperature stability. SSII shares 77.4% identity with the naturally psychrophilic protease subtilisin S41. Although SSII and S41 differ at 85 positions, four amino acid substitutions were sufficient to generate an SSII whose low temperature activity is greater than that of S41. That none of the four are found in S41 indicates that there are multiple routes to cold adaptation

Climate and Crop Yields Hand County

The County Pamphlet Series in Agricultural Economics is intended to make available to each county economic data concerning its farm history and present agricultural situation. It is hoped that these facts will be of use to county planning groups, individual farmers, research and extension workers and other persons interested in the agriculture of the counties. Each pamphlet will treat one subject for one county, and is to be released when completed. Pamphlets on various other economic subjects for the different counties will be prepared as soon as possible. A few copies of each pamphlet will be placed with the county extension agent and a limited number will be sent to private persons upon request. The project was initiated by the Department of Agricultural Economics and the work is under the direction of its regular staff

Climate and Crop Yields Tripp County

The County Pamphlet Series in Agricultural Economics is intended to make available to each county economic data concerning its farm history and present agricultural situation. It is hoped that these facts will be of use to county planning groups, individual farmers, research and extension workers and other persons interested in the agriculture of the counties. Each pamphlet will treat one subject for one county, and is to be released when completed. Pamphlets on various other economic subjects for the different counties will be prepared as soon as possible. A few copies of each pamphlet will be placed with the county extension agent and a limited number will be sent to private persons upon request. The project was initiated by the Department of Agricultural Economics and the work is under the direction of its regular staff

Climate and Crop Yields Clay County

The County Pamphlet Series in Agricultural Economics is intended to make available to each county economic data concerning its farm history and present agricultural situation. It is hoped that these facts will be of use to county planning groups, individual farmers, research and extension workers and other persons interested in the agriculture of the counties. Each pamphlet will treat one subject for one county, and is to be released when completed. Pamphlets on various other economic subjects for the different counties will be prepared as soon as possible. A few copies of each pamphlet will be placed with the county extension agent and a limited number will be sent to private persons upon request. The project was initiated by the Department of Agricultural Economics and the work is under the direction of its regular staff

Climate and Crop Yields Moody County

The County Pamphlet Series in Agricultural Economics is intended to make available to each county economic data concerning its farm history and present agricultural situation. It is hoped that these facts will be of use to county planning groups, individual farmers, research and extension workers and other persons interested in the agriculture of the counties. Each pamphlet will treat one subject for one county, and is to be released when completed. Pamphlets on various other economic subjects for the different counties will be prepared as soon as possible. A few copies of each pamphlet will be placed with the county extension agent and a limited number will be sent to private persons upon request. The project was initiated by the Department of Agricultural Economics and the work is under the direction of its regular staff

Climate and Crop Yields Marshall County

The County Pamphlet Series in Agricultural Economics is intended to make available to each county economic data concerning its farm history and present agricultural situation. It is hoped that these facts will be of use to county planning groups, individual farmers, research and extension workers and other persons interested in the agriculture of the counties. Each pamphlet will treat one subject for one county, and is to be released when completed. Pamphlets on various other economic subjects for the different counties will be prepared as soon as possible. A few copies of each pamphlet will be placed with the county extension agent and a limited number will be sent to private persons upon request. The project was initiated by the Department of Agricultural Economics and the work is under the direction of its regular staff