Vertebrate structural features

Brummendorf, T. and Rathjen, F. G. Axonal glycoproteins with immunoglobulin and fibronectin type II-related domains in vertebrates Structural features, binding activities and signal transduction. /. Neurochem. 61 1207-1219, 1993. 

Defensins, potent antimicrobial and proin-flammatory peptides antimicrobial peptides). Mammalian defensins are cationic peptides (Mr 3.5. 5 kDa), rich in lysine and arginine containing six cysteine residues which form three characteristic disulfide bridges. According to the alignment of the disulfide bonds and the overall structure, defensins can be divided into three groups a-defensins, /S-defensins, and 0-defensins. Antimicrobial peptides of plants or insects have also been termed defensins, though they have different structural features in comparison to vertebrate defensins. a-Defensins consist of... 

The selectivity of neonicotmoids for insect over vertebrate nAChRs is likely to result from selective recognition by insect uAChRs of its structural features and vice versa. To elucidate the mechanism of selectivity, structural features of neonicoti-noids and insect nAChRs contributing to this selectivity have been examined. 

The structural features responsible for the genotoxicity are a double bond in the necine base between C-1 and C-2, presence of hydroxy groups at C-1 and C-9, and esterification of at least one of these hydroxy groups with a branched carbon chain (Frei et al., 1992). In most vertebrates and insect herbivores, the alkaloid A -oxides are reduced in the gut to their free bases. The reduced alkaloids are then taken up and bioactivated by cytochrome P450-dependent monooxygenases of the liver to highly reactive dehydropyrrolizidine alkaloids that react with nucleophilic groups of proteins and DNA (Roder, 1995). 

The sialic acids are a family of ubiquitous aminosugars found in some bacteria and invertebrates, and in all vertebrate tissues. They are normally found as nonreducing termini of complex heteropolymers such as glycoproteins, glycopeptide hormones, and glycolipids. The chemistry and structural features of these compounds are described in Chapter 1 of this volume. 

Dimeric, trlmeric, and tetramerlc Interactions of ferritin subunits each have distinctive features which may relate to the function of the protein coat. Among vertebrates, at least, the amino acid sequence In such regions Is highly conserved, and forms structures which may have functional roles. 

Fish possess a large number of unique features that differentiate them both structurally and functionally from other vertebrates. Many of these biological features, including the gills, blood circulation and blood characteristics, and hepatic, renal, and digestive functions, are critical to drug pharmacokinetics. 

Many fundamental concepts in modem biology have been established through studies on aquatic organisms. Fish are of special interest to research workers, because some of their metabolic features characterized early vertebrates. Fish have also evolved numerous adaptations, which have permitted them not only to survive but also to thrive in recent times. The range of structural and functional adaptations and metabolic flexibility, combined with individual specializations, has resulted in an immense diversity of fish - more than 20 000 species - which greatly exceeds that of amphibians, reptiles, birds and mammals. As the final link in many food chains, fish can be reliable indicators of the condition of complex ecosystems. Studies on fish provide an understanding of the pathways of metabolic substances and of energy transformations in bodies... 

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