ABSTRACT
The structure of apo-azurin from Alcaligenes denitrificans has been determined at high resolution by X-ray crystallography. Two separate structure analyses have been carried out, (i) on crystals obtained from solutions of apo-azurin and (ii) on crystals obtained by removal of copper from previously formed crystals of holo-azurin. Data to 1.8 A resolution were collected from the apo-azurin crystals, by Weissenberg photography (with image plates) using synchrotron radiation and by diffractometry, and the structure was refined by restrained least-squares methods to a final R value of 0.160 for all data in the range 10.0-1.8 A. The final model of 1954 protein atoms, 246 water molecules (66 half-weighted), four SO(4)(2-) ions, and two low-occupancy (0.13 and 0.15) Cu atoms has r.m.s. deviations of 0.012, 0.045 and 0.013 A from standard bond lengths, angle distances and planar groups. For copper-removed azurin, data to 2.2 A were collected by diffractometry and the structure refined by restrained least squares to a final R value of 0.158 for all data in the range 10.0-2.2 A. The final model of 1954 protein atoms, 264 water molecules, two SO(4)(2-) ions, two low occupancy (0.18 and 0.22) metal atoms and one unidentified atom (modelled as S) has r.m.s. deviations of 0.013, 0.047 and 0.012 A from standard bond lengths, angle distances and planar groups. The two structures are essentially identical to each other and show no significant differences from the oxidized and reduced holo-azurin structures. The ligand side chains move slightly closer together following the removal of copper, with the radius of the cavity between the three strongly binding ligands, His 46, His 117 and Cys 112, shrinking from 1.31 A in reduced azurin to 1.24 A in oxidized azurin and 1.16 A in apo-azurin. There is a suggestion of increased flexibility in one of the copper-binding loops but the structure supports the view that the copper site found in holo-azurin is a stable structure, defined by the constraints of the polypeptide structure even in the absence of a bound metal ion.
ABSTRACT
BACKGROUND: The Child and Adolescent Trial for Cardiovascular Health is a school-based study designed to test the effectiveness of dietary, physical activity, and educational interventions for reducing cardiovascular disease risk and teaching healthful behaviors to children. METHODS: As part of a pilot phase in 1989, lipid, lipoprotein, and anthropometric measures were taken in black (n = 90), Hispanic (n = 68), and white (n = 265) 8- to 10-year-old schoolchildren in California, Louisiana, Minnesota, and Texas. RESULTS: There were no significant differences in mean lipoprotein cholesterol values between fasting and nonfasting children. Therefore data from fasting and nonfasting children were pooled. Males and females within the same ethnic groups had similar mean levels of total cholesterol, low-density lipoprotein cholesterol, and very low-density lipoprotein cholesterol. However, levels of high-density lipoprotein cholesterol were higher among white and black males than among females from the same ethnic groups. Black males had higher total cholesterol than white males and higher high-density lipoprotein cholesterol than white males and Hispanic males. Similarly, black females had higher high-density lipoprotein cholesterol than white and Hispanic females. In all children combined high-density lipoprotein cholesterol was inversely correlated and low-density lipoprotein cholesterol was positively correlated with subscapular and tricep skinfold thickness, weight, and body mass index. There were significant differences in mean lipoprotein cholesterol levels between geographic sites. Total cholesterol, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol were highest in children from California followed by children from Texas, Minnesota, and Louisiana. CONCLUSION: Our results suggest that body fatness total cholesterol, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol differ in children by gender, ethnicity, and geographic location.
