First class protein

Low-nitrogen (protein) diets have been advocated from the early years of treatment of severe chronic uremia. The very-low-protein diets tested in the MDRD Study were of marginal benefit in these well-supervised patients with very low renal function, but are not well adhered to in practice, may lead to negative nitrogen balance, and are not recommended. Protein intake is restricted spontaneously to approximately 0.6 to 0.8g/kg/day by uremic patients not receiving dietary advice. To prevent malnutrition, patients receive professional dietary advice, with diets containing an increased proportion of first class protein and increased calorie content of up to 35 kcal/kg/day. The NHANES III has confirmed an association with reduced GFR and malnutrition in noninstitutionalized individuals studied in a cross-sectional survey of more than 5000 participants stratified according to GFR. ... 

Plant genetic experiments presently being undertaken with corn (maize) and with rice may improve the nutritional properties of these cereals. These may help to close the amino acid nutritional gap, which exists between plant sources of proteins and first class proteins [70]. However, this will still not remove the need for synthetic amino acids for their many other uses (e.g., for chelating agents), as dietary supplements, as building blocks for specialty proteins, and as components of intravenous feeding solutions. All of these... 

Amino acid nutrition, however, is not just an issue for third-world countries. For various reasons people in more affluent societies restrict their diets, and vegetarian and vegan diets may contain insufficient quantities of first class protein. This is for rather similar reasons to the maize problem. Vegetarians often rely heavily on beans for their supply of protein, and beans, like maize, contain large amounts of single storage proteins intended for the young plant. It is risky, therefore to rely too heavily on one kind of bean. Varied sources of protein are essential for health. 

Essential amino acids cannot be synthesized because the liver is deficient in at least one of the enzymes involved in the analogous plant pathway. Therefore, the carbon skeleton of the essential amino acid but not necessarily the complete amino acid must be supplied in the diet. Proteins from animal sources, e.g. meat, milk and eggs, are very effective in the support of maintenance and growth of rats and man and are classified as first-class proteins . Others, frequently from plant sources, do not contain all the essential components and are called second-class proteins . A second-class protein may lack, or contain inadequate quantities of, one or several amino acids. 

The first elastomeric protein is elastin, this structural protein is one of the main components of the extracellular matrix, which provides stmctural integrity to the tissues and organs of the body. This highly crosslinked and therefore insoluble protein is the essential element of elastic fibers, which induce elasticity to tissue of lung, skin, and arteries. In these fibers, elastin forms the internal core, which is interspersed with microfibrils [1,2]. Not only this biopolymer but also its precursor material, tropoelastin, have inspired materials scientists for many years. The most interesting characteristic of the precursor is its ability to self-assemble under physiological conditions, thereby demonstrating a lower critical solution temperature (LCST) behavior. This specific property has led to the development of a new class of synthetic polypeptides that mimic elastin in its composition and are therefore also known as elastin-like polypeptides (ELPs). 

Sequence data, in combination with functional studies, reveal several classes of E-IIs as shown in Fig. 3. These classes will most likely change and expand as future studies define additional domains with new functions. We introduce it here, only for the sake of our own convenience, in this chapter. The first class is represented by E. coli II . This protein is unique in that, as yet, it is the only representative of its class. It consists only of a single hydrophobic peptide with no hydrophilic domain attached at either end [7,9]. 

In bacteria, accumulation of substrates against a concentration gradient can occur through two main classes of transport systems (see [30] for a summary). The prototype of the first class of transporters is the /3-galactoside permease of Escherichia coli (see [31]). It is a relatively simple system involving only a single membrane-bound protein. It catalyzes a lactose-H symport. Other transporters... 

Proteins fall into three classes when characterized with mass spectrometry proteins whose complete sequence is given in a database, proteins whose sequence is partially represented in expressed sequence tag databases, and proteins whose sequence is unknown. Proteins of the first class can be identified by peptide mass mapping in a very high through-... 

Before plunging into a discussion of how such complexes are prepared, it is perhaps worthwhile to consider explicitly the rationale for such activity. The synthesis and characterization of accurate model complexes for a given metal site in a protein or other macromolecule allows one to (l) determine the intrinsic properties of the metal site in the absence of perturbations provided by the protein environment or (il) in favorable cases, deduce the structure of the metal site by comparison of corresponding physical and spectroscopic properties of the model and metalloprotein (3). The first class of model complexes has been termed "corroborative models" by Hill (4), while the second are termed "speculative models" (4). To date, virtually all the major achievements of the synthetic model approach have been in development of corroborative models. 

Starting from the activated Jak kinases, a signaling pathway leads directly to transcription factors that are phosphorylated by the Jak kinases on tyrosine residues and activated for stimulation of transcription (review Horvath and Darnell, 1997). These transcription factors belong to a class of proteins known as Stat proteins (Stat = signal transducer and activator of transcription). At least seven different Stat proteins are known (Statl-4, StatSa, StatSb, Stat6). The first Stat proteins, Statl and Stat2, were foimd in association with signal transduction via interferon y. 

Poly(esters) (Table 11.2) are the first class of polymers discussed, as they are the most widely investigated of all of the polymer families for oral protein delivery. Poly(esters) used for oral drug delivery have primarily been biodegradable polymers (Figure 11.1). Biodegradation is the primary delivery mechanism for poly(ester) polymers used for protein and peptide delivery. The degradation properties of poly(esters) are dependent on the monomers used to produce the poly(ester). Several poly(esters) are discussed in detail in the following sections. 

Beckwith and his colleagues isolated a large family of mutants that were permanently catabolite-repressed. These mutants fell into two categories Those that could be pheno-typically corrected by growing in the presence of cAMP and those that could not. The first class of mutants were believed to be defective in the synthesis of cAMP, and the latter class were presumed to be defective in the protein receptor for cAMP. Cell-free extracts were prepared from... 

The first class of membranous calcium binding proteins are represented by those proteins involved in the generation and modulation of the calcium signal (Table III). The calcium signal is regulated by the uptake and release of calcium across the three major membrane systems which bound the cytoplasm (the plasma membrane, the... 

The first class is cupredoxins—single-domain blue copper proteins composed of only one BCB domain. These proteins include plastocyanin, azurin, pseudoazurin, amicyanin, auracyanins, rusticyanin, halocyanin, and sulfocyanin (see Section IV). Plantacyanin of the phytocyanin family (Section V), subunit II of the cytochrome c oxidase, and the recently characterized nitrosocyanin also fall into this class. The last two are single BCB domain polypeptides closely related structurally to cupredoxins, but harboring, respectively, a binuclear copper site known as CuA and a novel type of copper-binding site called red (see Sections IX and X). 

There are several major functional classes of EF-hand proteins. In the first class, trigger proteins like CaM and TnC bind calcium with a large change in protein... 

---