ABSTRACT
Calcineurin B homologous protein 1 (CHP1), also known as p22, is a calcium-binding EF-hand protein that plays a role in membrane trafficking. It binds to multiple effector proteins, including Na(+)/H(+) exchangers, a serine/threonine kinase, and calcineurin, potentially modulating their function. The crystal structure of calcium-bound CHP1 from rat has been determined at 2.2 Angstroms of resolution. The molecule has a compact alpha-helical structure containing four EF-hands. The overall folding topology of the protein is similar to that of the regulatory B subunit of calcineurin and to that of calcium- and integrin-binding protein. The calcium ion is coordinated in typical fashion in the third and fourth EF-hands, but the first and second EF-hands contain no calcium ion. The first EF-hand is maintained by internal interactions, and the second EF-hand is stabilized by hydrophobic interactions. CHP1 contains a hydrophobic pocket on the opposite side of the protein to the EF-hands that has been implicated in ligand binding.
Subject(s)
Calcineurin/chemistry , Calcium-Binding Proteins/chemistry , Lipoproteins/chemistry , Amino Acid Motifs , Amino Acid Sequence , Animals , Calcium/chemistry , Calcium/metabolism , Calcium-Binding Proteins/metabolism , Crystallography, X-Ray , DNA, Complementary/metabolism , Ions , Ligands , Lipoproteins/metabolism , Models, Molecular , Molecular Sequence Data , Peptides/chemistry , Protein Binding , Protein Conformation , Protein Folding , Protein Structure, Secondary , Protein Structure, Tertiary , Protein Transport , Rats , Sequence Homology, Amino Acid , UltracentrifugationABSTRACT
The angiotensin-converting enzyme (ACE) DD genotype is associated with exaggerated pulmonary hypertension and disturbance in tissue oxygenation during exercise in patients with chronic obstructive pulmonary disease (COPD). This study was designed to examine the acute effects of nifedipine administration in pulmonary haemodynamics and oxygen delivery during exercise in COPD patients with II, ID, and DD genotypes. Thirty-three COPD patients (II = 12, ID = 11, DD = 10) with placebo or nifedipine (10 mg) underwent right heart catheterization with exercise, and systemic and pulmonary haemodynamic variables were examined. At rest, there was no significant difference in either mean pulmonary arterial pressure (mPAP), pulmonary vascular resistance (PVR) or oxygen delivery (DO2) among the three groups. However, the magnitude of mPAP or PVR after exercise was the DD > ID > II genotype. In contrast, the magnitude of DO2 after exercise was the II > ID > DD genotype. We also found that nifedipine administration significantly decreased mPAP after exercise in all the three groups. However, we found no significant difference in PVR or DO2 between placebo and nifedipine administration in all the three groups. Thus, a single administration of nifedipine may not have the clinical efficacy for the treatment of pulmonary hypertension and impaired oxygen delivery during exercise in COPD patients with different ACE gene polymorphisms.