The factor IX gene is primarily expressed in the liver and the factor IX gene product has a multidomain structure (Fig. 2). The first and second domains are a signal peptide and propeptide, respectively. These are cleaved to produce the mature protein that is secreted as a 415 amino acid single-chain peptide. Factor IX undergoes extensive posttranslational modification and the N-terminal domain of mature factor IX contains 12 g-carboxyglutamic residues; this ''Gla'' domain is important for phospholipid binding. This is followed by two EGF-like domains and an activation peptide (a 36-amino acid region that includes two cleavage sites required for activation of factor IX). The C-terminal catalytic domain is responsible for the proteolysis of factor X to factor Xa, and has substantial sequence homology to other vitamin K-dependent serine proteases. During activation, factor IX cleavage results in a light chain and a heavy chain, held together by disulfide bonds. Structural data is available for factor IX and some of its interactions1-6-1 and this has been extended by molecular modeling studies.
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The use of dumbbells gives you a much more comprehensive strengthening effect because the workout engages your stabilizer muscles, in addition to the muscle you may be pin-pointing. Without all of the belts and artificial stabilizers of a machine, you also engage your core muscles, which are your body's natural stabilizers.