Activation of type II calcium/calmodulin-dependent protein kinase by Ca^(2+)/calmodulin is inhibited by autophosphorylation of threonine within the calmodulin-binding domain

It is now well established that autophosphorylation of a threonine residue located next to each calmodulin-binding domain in the subunits of type II Ca^(2+)/calmodulin-dependent protein kinase causes the kinase to remain active, although at a reduced rate, after Ca^(2+) is removed from the reaction. This autophosphorylated form of the kinase is still sensitive to Ca2+/calmodulin, which is required for a maximum catalytic rate. After removal of Ca^(2+), new sites are autophosphorylated by the partially active kinase. Autophosphorylation of these sites abolishes sensitivity of the kinase to Ca^(2+)/calmodulin (Hashimoto, Y., Schworer, C. M., Colbran, R. J., and Soderling, T. R. (1987) J. Biol. Chem. 262, 8051-8055). We have identified two pairs of homologous residues, Thr^(305) and Ser^(314) in the alpha subunit and Thr^(306) and Ser^(315) in the beta subunit, that are autophosphorylated only after removal of Ca^(2+) from an autophosphorylation reaction. The sites were identified by direct sequencing of labeled tryptic phosphopeptides isolated by reverse-phase high pressure liquid chromatography. Thr^(305-306) is rapidly dephosphorylated by purified protein phosphatases 1 and 2A, whereas Ser^(314-315) is resistant to dephosphorylation. We have shown by selective dephosphorylation that the presence of phosphate on Thr^(305-306) blocks sensitivity of the kinase to Ca^(2+)/calmodulin. In contrast, the presence of phosphate on Ser^(314-315) is associated with an increase in the Kact for Ca^(2+)/calmodulin of only about 2-fold, producing a relatively small decrease in sensitivity to Ca^(2+)/calmodulin

ANALYSIS OF BORROWER AND LENDER USE OF INTEREST ASSISTANCE ON FSA GUARANTEED FARM LOANS

The Farm Security and Rural Investment Act of 2002 made permanent the interest assistance program for the Farm Service Agency's guaranteed loans, authorized a significant increase in funding for the program, and targeted funding for beginning farmers and ranchers. The research presented here provides a basic descriptive analysis of past use. In particular, borrower data for Federal fiscal years 1985 through 2002 are examined in several dimensions. These dimensions include geographic, borrower type, lender type, interest rate differentials, percent guarantee, and the status of the loan as to whether a loss claim was paid or the loan remained active. Even though the program has been in existence for more than 15 years, little is known about its impact and utilization. This research is an initial step in documenting usage of the program.Agricultural and Food Policy, Agricultural Finance,

National Transonic Facility status

The National Transonic Facility (NTF) was operational in a combined checkout and test mode for about 3 years. During this time there were many challenges associated with movement of mechanical components, operation of instrumentation systems, and drying of insulation in the cryogenic environment. Most of these challenges were met to date along with completion of a basic flow calibration and aerodynamic tests of a number of configurations. Some of the major challenges resulting from cryogenic environment are reviewed with regard to hardware systems and data quality. Reynolds number effects on several configurations are also discussed

Intraday credit: risk, value, and pricing

An abstract for this article is not availableElectronic funds transfers ; Payment systems ; Overdrafts

Evaluation of Three Rations on Growth and Reproductive Performance for Replacement Heifers

Nutrition following weaning of replacement heifers affects their performance as cows. Low levels of energy can delay puberty and reduce conception rates. Excessively high levels can decrease milk production and life span. Previous research indicates that gains should be kept to about 220 pounds from weaning to first breeding. This level of gain precludes high concentrate rations, curtailing flexibility and ability to minimize feed costs when concentrates are a cheaper source of energy. Limiting feed intake to supply desired total energy consumption would allow flexibility and use of higher percentage grain when economical. Limit feeding has been studied with finishing cattle regarding its influence on digestibility of feed stuffs. Limit feeding has been used to produce desired gains in heifers but not studied as a possible feeding program for replacement heifers. This study was conducted to determine if the use of rations containing various energy levels with intake limited could be successfully used to raise replacement heifers