Crystallization and preliminary crystallographic analysis of tetrahydrodipicolinate-N-succinyltransferase.

Crystals of tetrahydrodipicolinate-N-succinyltransferase have been obtained from solutions containing 2-propanol and polyethylene glycol 4,000. These crystals belong to the monoclinic space group P2(1), diffract X-rays to a resolution of 2.2 A, and contain one trimer per asymmetric unit.

The use of physician services under a national health insurance scheme. An examination of the Canada Health Survey.

In this paper the individual is employed as the unit of analysis to examine the extent to which the use of physician care by beneficiaries insured under the Canadian Medicare program is determined by medical needs and sociodemographic characteristics as opposed to economic considerations. The data were derived from the Canada Health Survey, which is a stratified, multistaged sample of the entire population. The results of the discriminant and weighted multiple regression analysis indicate that the use or nonuse of service and the volume of physician care consumed is determined by medical needs and sociodemographic characteristics rather than by economic status. Accordingly, the findings of this study are consistent with the contention that the Medicare program has resulted in an equitable distribution of physician service.

Three-dimensional structure of tetrahydrodipicolinate N-succinyltransferase.

The conversion of tetrahydrodipicolinate and succinyl-CoA to N-succinyltetrahydrodipicolinate and CoA is catalyzed by tetrahydrodipicolinate N-succinyltransferase and is the committed step in the succinylase pathway by which bacteria synthesize L-lysine and meso-diaminopimelate, a component of peptidoglycan. The X-ray crystal structure of THDP succinyltransferase has been determined to 2.2 A resolution and has been refined to a crystallographic R-factor of 17.0%. The enzyme is trimeric and displays the left-handed parallel beta-helix (L beta H) structural motif encoded by the "hexapeptide repeat" amino acid sequence motif [Raetz, C.R.H., & Roderick, S.L. (1995) Science 270, 997-1000]. The approximate location of the active site of THDP succinyltransferase is suggested by the proximity of binding sites for two inhibitors: p-(chloromercuri)benzenesulfonic acid and cobalt ion, both of which bind to the L beta H domain.

Trypanosoma congolense: structure and molecular organization of the surface glycoproteins of two early bloodstream variants.

The complete primary structures of two variant specific glycoproteins (VSGs) of the nannomonad Trypanosoma (N.) congolense are presented. These coat proteins subserve the function of antigenic variation. The secondary structure potentials of both VSGs have been calculated. The amino acid sequences and secondary structure potentials of these VSGs have been compared with the primary structures and secondary structure potentials of several Trypanosoma brucei complex VSGs. In homologous regions, the T. brucei complex VSGs show a pattern of sharply contrasting secondary structure potentials. It has been suggested previously that this pattern gives rise to different folding structures in different members of this polygene protein family. Thus, different short regions of the polypeptide sequence are exposed as antigenic "caps" on the solvent-exposed surface of intact trypanosomes. A sharply contrasting secondary structure potential pattern is also found in regions of the two T. congolense VSGs. However, there is little homology of primary structure between each of the two T. congolense VSGs and any member of the T. brucei complex VSG polygene family whose primary structure has been determined.