User:Michael Adams/Sandbox 1: Difference between revisions
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In Strong and Ellington’s 1994 experiment, arginine kinase (AK) was isolated from Limulus polyphemus, the Atlantic horseshoe crab, a marine chelicerate arthropod (Strong and Ellington, 1994). They isolated the gene for AK, sequenced the DNA and identified it to be 1071 nucleotides. The 1071 nucleotides produce a 357 amino acid protein and AK extracted from other organisms show similarity to this protein. AK serves a similar function to that of creatine kinase, in vertebrates (Strong and Ellington, 1994). The enzyme creatine kinase maintains energy homeostasis by producing ATP in high energy requiring cells such as skeletal and cardiac muscle and neurons (Wallimann et al, 1998). This is done by the transfer of an N-phosphoryl group from phosphocreatine to ADP. | In Strong and Ellington’s 1994 experiment, arginine kinase (AK) was isolated from Limulus polyphemus, the Atlantic horseshoe crab, a marine chelicerate arthropod (Strong and Ellington, 1994). They isolated the gene for AK, sequenced the DNA and identified it to be 1071 nucleotides. The 1071 nucleotides produce a 357 amino acid protein and AK extracted from other organisms show similarity to this protein. AK serves a similar function to that of creatine kinase, in vertebrates (Strong and Ellington, 1994). The enzyme creatine kinase maintains energy homeostasis by producing ATP in high energy requiring cells such as skeletal and cardiac muscle and neurons (Wallimann et al, 1998). This is done by the transfer of an N-phosphoryl group from phosphocreatine to ADP. | ||
== Structure == | == Structure == | ||
The structure of arginine kinase is mainly α-helical and contains an N-terminal region with a specificity loop for specific substrate binding. (Figure 1b). However, when compared to creatine kinase, arginine kinase is not terminated at the N-terminal end with a pair of proline-glycine residues. Typically within creatine kinase, the proline molecules restrict changes in conformation and is the amino acid that terminates helices. The glycine chains are usually associated with flexibility. However, in arginine kinase this is typically not the case. On the C-terminal end, there is an eight-stranded antiparallel β-sheet with seven α-helices flanking the sheet (Figure 1). [[Image:F1.large.jpg]] | The structure of arginine kinase is mainly α-helical and contains an N-terminal region with a specificity loop for specific substrate binding. (Figure 1b). However, when compared to creatine kinase, arginine kinase is not terminated at the N-terminal end with a pair of proline-glycine residues. Typically within creatine kinase, the proline molecules restrict changes in conformation and is the amino acid that terminates helices. The glycine chains are usually associated with flexibility. However, in arginine kinase this is typically not the case. On the C-terminal end, there is an eight-stranded antiparallel β-sheet with seven α-helices flanking the sheet (Figure 1). [[Image:F1.large.jpg]] [[Image:http://www.rcsb.org/pdb/images/3M10_bio_r_500.jpg?bioNum=1]] | ||
The small domain specificity loop forms a “specificity” pocket surrounding the methyl substituent of the guanidinium group that is unique to creatine substrates. In this region, five residues differ between arginine and creatine kinases: 312, 314, 315, 317, and 319 (Newsholme et al, 1978). Within each arginine kinase, there is typically a Mg+2 ion adjacent to the antiparallel β-sheet (Figure 1b). Typically two arginine kinase structures mirror each other and form a hole like structure in between the two. However, when a substrate is in the binding site, the active site remains unchanged and does not change in conformation (Figure 1a). | The small domain specificity loop forms a “specificity” pocket surrounding the methyl substituent of the guanidinium group that is unique to creatine substrates. In this region, five residues differ between arginine and creatine kinases: 312, 314, 315, 317, and 319 (Newsholme et al, 1978). Within each arginine kinase, there is typically a Mg+2 ion adjacent to the antiparallel β-sheet (Figure 1b). Typically two arginine kinase structures mirror each other and form a hole like structure in between the two. However, when a substrate is in the binding site, the active site remains unchanged and does not change in conformation (Figure 1a). | ||
