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Acyl carrier protein (ACP) is an essential cofactor in biosynthesis of fatty acids and many other reactions that require acyl transfer steps. We have determined the first crystal structures of an acylated form of ACP from E. coli, that of butyryl-ACP. Our analysis of the molecular surface of ACP reveals a plastic hydrophobic cavity in the vicinity of the phosphopantethylated Ser36 residue that is expanded and occupied by the butyryl and beta-mercaptoethylamine moieties of the acylated 4'-phosphopantetheine group in one of our crystal forms. In the other form, the cavity is contracted, and we propose that the protein has adopted the conformation after delivery of substrate into the active site of a partner enzyme.

The proteins of the primary cell walls of suspension cultured cells of five plant species, Arabidopsis, carrot, French bean, tomato, and tobacco, have been compared. The approach that has been adopted is differential extraction followed by SDS-polyacrylamide gel electrophoresis (PAGE), rather than two-dimensional gel analysis, to facilitate protein sequencing. Whole cells were washed sequentially with the following aqueous solutions, CaCl 2 , CDTA (cyclohexane diaminotetraacetic acid, DTT (dithiothreitol), NaCl, and borate. SDS-PAGE analysis showed consistent differences between species. From the 233 proteins that were selected for sequencing, 63% gave N-terminal data. This analysis shows that (i) patterns of proteins revealed by SDS-PAGE are strikingly different for all five species, (ii) a large number of these proteins cannot be identified by data base searches indicating that a significant proportion of wall proteins have not been previously described, (iii) the major proteins that can be identified belong to very different classes of proteins, (iv) the majority of proteins found in the extracellular growth media are absent from their respective cell wall extracts, and (v) the results of the extraction process are indicative of higher order structure. It appears that aspects of speciation reside in the complement of extracellular wall proteins. The data represent a protein resource for cell wall studies complementary to EST (expressed sequence tag) and DNA sequencing strategies.The plant cell wall is a dynamic system generally considered to be composed of more than 90% carbohydrate polymers. Proteins, phenolics and possibly lipids make up the remainder of the wall (1-3). To date, most research interest has been in the carbohydrate components because of considerations of their structural role and commercial interest. This has led to a number of models for the integration, interpolymeric association, and assembly of the wall (3, 4). By comparison, our knowledge of the complexity of protein in the plant cell wall is in a less advanced state. Much of the understanding of the range of structural wall proteins has come from cDNA and genomic cloning exercises and has led to the identification of glycine-, cysteine-, proline-, and hydroxyproline-rich subsets of wall proteins. In addition, many extracellular enzymes have been identified that are required for the restructuring and modification of this dynamic extracellular matrix which underpin its role in defense, detoxification, signaling, cell-cell recognition, cell expansion, cell adhesion, cell separation, translocation, differentiation, and morphogenesis (2, 5, 6). However, there is a lack of direct studies on the proteins themselves and the true range of extracellular proteins and their species differences remains to be elucidated. The present work describes the systematic extraction and sequencing of the major primary wall proteins from five species representing four families of plants.Since whole plant tissue is complicated by the presence of different tissue...

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Four neurotoxic polypptidcs were purified from the venom of the South American 'armed' spider Phuncmiu nigrivenrer (Keys) by gel filtration and rcvcrse phase FPLC and HPLC. These cystcine-rich polypcptidcs exhibited dimerent lcvcls of neurotoxicity in mice after intraccrebrovcntricular injection. Tic'-I, TxZ5 and Tx2-6 caused spastic paralysis nnd deuh, but the less toxic Tx2-9 produced only tail erection and scratching. The molecular weights of the polypeptides as determined by desorption mass spectroscoopy were 5838.8 for Tx2-1, 5116.6 (Txl-5). 5291.3 (Tx2-6) and 3742.1 (Tx2-9). The complele amino acid sequences of the neurotoxins were determhxd by automnted Edman degradation and by manual DABITC-PITC microscqeuncc analysis of peptidcs obtained atIer digestions with various proteases. The amino acid sequences ofTx2.1 (53 residue), Tx2-5 (49 residues) and Tx2-6 (48 residues) were homologous, but had only limited similarities to the less toxic Tx2-9 (32 residues). All four polypeptides bad varying seqlxnce identities with other neurotoxins from different spider species and biologiiwlly active peptides from scorpions, a sea snail and seeds of Mirrrliitijufupa.Spider venom; Amino acid xquence; Neuroloxin; Phoneutriu rri~rivwkr