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Journal Issue - Volume 4 Issue 9 (September 1995)

Abstract Hyaluronan is an important constituent of the extracellular matrix. This polysaccharide can be hydrolyzed by various hyaluronidases that are widely distributed in nature. The structure of some bacterial and animal enzymes of this type has recently been elucidated. It could be shown that the hyaluronidases from bee and hornet venom and the PH‐20 hyaluronidase present on mammalian spermatozoa are homologous proteins. ...

Abstract We attempted to predict through computer modeling the structure of the light‐harvesting complex II (LH‐II) of Rhodospirillum molischianum, before the impending publication of the structure of a homologous protein solved by means of X‐ray diffraction. The protein studied is an integral membrane protein of 16 independent polypeptides, 8 α‐apoproteins and 8 β‐apoproteins, which aggregate and bind to 24 bacteriochlorophyll‐a's and 12 lyco‐penes....

Abstract The fourth EGF‐like domain of thrombomodulin (TM4), residues E346‐F389 in the TM sequence, has been synthesized. Refolding of the synthetic product under redox conditions gave a single major product. The disulfide bonding pattern of the folded, oxidized domain was (1–3, 2–4, 5–6), which is the same as that found in EGF protein. TM4 was tested for TM anticoagulant activity because deletion and substitution mutagenesis...

Abstract Motifs in ligand‐binding domains of the neurotrophin (NTR) and lymphotoxin (TNFR‐I) receptors define a family of receptors that mediates programmed cell death. We have explored relationships of architecture and function in this family through a molecular model of NTR, also called p75NGFR or LANR. Modeling by homology took advantage of four modular subdomains in the crystal structure of TNFR‐1 that also occur in NTR....

Abstract The main functions of the T‐cell receptor (TCR) involve its specific interaction with short and linear antigenic peptides bound to the major histocompatibility complex (MHC) molecules. In the absence of a 3D structure for TCR and for the TCR/peptide/MHC complex, several attempts to characterize the structural components of the TCR/peptide/MHC interaction have been made. However, this subject is still troublesome. ...

Abstract The heat‐stable enterotoxin b (STb) is secreted by enterotoxigenic Escherichia coli that cause secretory diarrhea in animals and humans. It is a 48‐amino acid peptide containing two disulfide bridges, between residues 10 and 48 and 21 and 36, which are crucial for its biological activity. Here, we report the solution structure of STb determined by two‐ and three‐dimensional NMR methods. Approximate interproton distances derived from...

Abstract The structure of human pancreatic α‐amylase has been determined to 1.8 Å resolution using X‐ray diffraction techniques. This enzyme is found to be composed of three structural domains. The largest is Domain A (residues 1–99, 169–404), which forms a central eight‐stranded parallel β‐barrel, to one end of which are located the active site residues Asp 197, Glu 233, and Asp 300. Also found in this vicinity is a bound chloride...

Abstract The tyrosine (eTATase) and aspartate (eAATase) aminotransferases of Escherichia coli transaminate dicarboxylic amino acids with similar rate constants. However, eTATase exhibits ∼102‐104‐fold higher second‐order rate constants for the transamination of aromatic amino acids than does eAATase. A series of natural and unnatural amino acid substrates was used to quantitate specificity differences for these two highly related enzymes. A ...

Abstract Although several high‐resolution X‐ray crystallographic structures have been determined for Escherichia coli aspartate aminotransferase (eAATase), efforts to crystallize E. coli tyrosine aminotransferase (eTATase) have been unsuccessful. Sequence alignment analyses of eTATase and eAATase show 43% sequence identity and 72% sequence similarity, allowing for conservative substitutions. The high similarity of the two sequences indicates ...

Abstract We have cloned and expressed microplasminogen (mPlg), consisting of the N‐terminal undecapeptide of human glu‐P/g spliced to its proenzyme domain. This truncated (∼28 kDa) proenzyme retained the distinctive catalytic activities of the larger parent. Replacement of M residues followed by M shuffling permitted subsequent scission by site‐directed chemical proteolysis (in CNBr/formic acid) without impairing any of the protein's...

Abstract We have used a group of human microplasminogens (mPlg), modified by residue substitutions, insertions, deletions, and chain breaks (1) to study the determinants of productive interactions with two plasminogen activators, urokinase (uPA), and streptokinase (SK); (2) to explore the basis of species specificity in the zymogen‐SK complex activity; and (3) to compare active SK complex formation in mPlg and microplasmin (mPlm). Modifications within the...

Abstract We present an efficient new algorithm that enumerates all possible conformations of a protein that satisfy a given set of distance restraints. Rapid growth of all possible self‐avoiding conformations on the diamond lattice provides construction of α‐carbon representations of a protein fold. We investigated the dependence of the number of conformations on pairwise distance restraints for the proteins crambin, pancreatic trypsin...

Abstract The activation process of porcine pancreatic procarboxypeptidase B (pro‐CPB) has been studied in detail by a number of complementary methodologies, and a description of the molecular events that lead to the generation of active carboxypeptidase B (CPB) has been deduced. The generated CPB participates in the degradation of its own activation segment by excising C‐terminal residues from fragments produced by tryptic...

Abstract SpoOF, sporulation stage 0 F protein, a 124‐residue protein responsible, in part, for regulating the transition of Bacillus subtilis from a vegetative state to a dormant endospore, has been studied by high‐resolution NMR. The 1H, 15N, and 13C chemical shift assignments for the backbone residues have been determined from analyses of 3D spectra, 15N TOCSY‐HSQC, 15N NOESY‐HSQC, HNCA, and HN(CO)CA. Assignments for many side‐chain proton resonances are also...

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