The intrinsic pathway requires the clotting factors VIII, IX, X, XI, and XII. Also required are the proteins prekallikrein (PK) and high-molecular-weight kininogen (HK or HMWK), as well as calcium ions and phospholipids secreted from platelets. The role of PK and HMWK is described in the above section. Each of these pathway constituents leads to the conversion of factor X (inactive) to factor Xa. Initiation of the intrinsic pathway occurs when prekallikrein, high-molecular-weight kininogen, factor XI and factor XII are exposed to a negatively charged surface. This is termed the contact phase and can occur as a result of interaction with the phospholipids (primarily phosphatidylethanolamine, PE) of circulating lipoprotein particles such as chylomicrons, VLDLs, and oxidized LDLs. This is the basis of the role of hyperlipidemia in the promotion of a pro-thrombotic state and the development of atherosclerosis.
Erythrocyte membrane proteins are redistributed at the time of junction formation so that the contact area is free of erythrocyte membrane proteins. A merozoite serine protease which cleaves erythrocyte band 3 has been described ( Braun-Breton 1993 ). Because of the pivotal role band 3 plays in the homeostatis of the submembrane skeleton, its degradation could result in a localized disruption of the cytoskeleton. Reorganization of the submembrane cytoskeleton and lipid architecture probably accompanies merozoite invasion ( Zuccala 2011 ).
The regulatory domains of cPKC isoforms (cPKCα: cPKC-alpha; cPKCβI: cPKC-beta I, cPKCβII: cPKC-beta II; and cPKCγ: cPKC-gamma) contain a C1 domain consisting of tandem ~50 amino acid long sequences termed C1A and C1B. The C1A and C1B subdomains each have six cysteines and two histidines that coordinate two Zn 2+ ions. The cPKCβII enzyme is an alternatively spliced version of cPKCβI. The C1A/C1B motifs function as a DAG-/PMA-binding motif (PMA: phorbol myristic acid). The regulatory domains of the cPKC isoforms also contain a C2 domain that binds anionic phospholipids in a calcium-dependent manner. All the cPKC isoforms require DAG, Ca 2+ , and phospholipids for activation.