Calcium binding protein parvalbumin

We now consider two calcium binding proteins, parvalbumin and troponin. The first, carp parvalbumin, is a small protein of known crystal structure.41 It binds two Ca2+ ions per molecule. One of the Ca2+ ions is essential for a folded structure to be maintained the second may be lost with a relatively small conformational change.42... 

These are soluble, sarcoplasmic calcium-binding proteins found in vertebrates. Invertebrates contain different sarcoplasmic calcium-binding proteins. Parvalbumins are low molecular weight (10 000-12 000), acidic proteins which contain two binding sites for Ca. The structure of parvalbumin has been determined, and details of the calcium sites are given in Table 6. XANES studies indicate that the calcium sites are similar to those in calmodulin, but different from... 

Kosaka K, Heizmann CW, Kosaka T. 1994a. Calcium-binding protein parvalbumin-immunoreactive neurons in the rat olfactory bulb. 1. Distribution and structural features in adult rat. Exp Brain Res 99 191-204. 

Toida K, Kosaka K, Heizmann CW, Kosaka T 1994. Synaptic contacts between mitral/tufted cells and GABAergic neurons containing calcium-binding protein parvalbumin in the rat olfactory blob, with special reference to reciprocal synapses between them. Brain Res 650 347-352. 

Celio MR, Heizmann CW (1981) Calcium binding protein parvalbumin as a neuronal marker. Nature... 

Basket/stellate cells could be identified by their expression of the calcium-binding protein, parvalbumin. 

The retrograde BDA labeling of pyramidal neurons, described in Sect. 3.1, can be easily combined with the immunohistochemical detection of several molecules. Here we describe the combination of the retrograde BDA tracing with the immunohistochemistry for the calcium binding protein calbindin. In the neocortex, the three calcium binding proteins parvalbumin, calbindin, and calretinin... 

Nonrepetitive but well-defined structures of this type form many important features of enzyme active sites. In some cases, a particular arrangement of coil structure providing a specific type of functional site recurs in several functionally related proteins. The peptide loop that binds iron-sulfur clusters in both ferredoxin and high potential iron protein is one example. Another is the central loop portion of the E—F hand structure that binds a calcium ion in several calcium-binding proteins, including calmodulin, carp parvalbumin, troponin C, and the intestinal calcium-binding protein. This loop, shown in Figure 6.26, connects two short a-helices. The calcium ion nestles into the pocket formed by this structure. 

It should be pointed out that the addition of substances, which could improve the biocompatibility of sol-gel processing and the functional characteristics of the silica matrix, is practiced rather widely. Polyethylene glycol) is one of such additives [110— 113]. Enzyme stabilization was favored by formation of polyelectrolyte complexes with polymers. For example, an increase in the lactate oxidase and glycolate oxidase activity and lifetime took place when they were combined with poly(N-vinylimida-zole) and poly(ethyleneimine), respectively, prior to their immobilization [87,114]. To improve the functional efficiency of entrapped horseradish peroxidase, a graft copolymer of polyvinylimidazole and polyvinylpyridine was added [115,116]. As shown in Refs. [117,118], the denaturation of calcium-binding proteins, cod III parvalbumin and oncomodulin, in the course of sol-gel processing could be decreased by complexation with calcium cations. 

Table XI (346-390) lists a number of calcium-binding proteins and indicates very succinctly their role in biological systems. This table both illustrates the range of functions of calcium-binding proteins and serves to introduce those which appear subsequently in this chapter. The structures and functions of particularly important calcium-binding proteins such as calmodulin, parvalbumin, and troponin C are described in standard texts on biochemistry. The minimal Table XI entry for the particularly important calmodulins is amplified in the next paragraph. Table XI provides a sprinkling of references to enable readers to gain entry into the literature, for these and for most of the less-familiar species.

A protein of similar molecular weight to that of rat oncomodulin, rat and rabbit parvalbumins, S100, and the vitamin D-dependent calcium-binding proteins has been isolated from chicken gizzard smooth muscle. In this case, however, the fluorescence emission from the four tyrosine residues is quenched by Ca2+ binding.(160) The decrease in fluorescence intensity was used to suggest that there are two different classes of Ca2+binding sites. 

J. P. MacManus, D. C. Watson, and M. Yaguchi, The complete amino acid sequence of oncomodulin—a parvalbumin-like calcium-binding protein from Morris hepatoma 5123tc, Eur. J. Biochem. 136, 9-17 (1983). 

In order to understand these effects in a detailed way for the calcium-binding proteins, it is necessary to compare the structure of the calcium-free and calcium-bound forms of each protein. The structures of parvalbumin and the intestinal calcium-binding protein (Wasserman protein) are known (see Table 6), but at present there are no crystal structures available for calcium-free proteins. Some structural information has been deduced from changes in the NMR spectrum as calcium is removed from the calcium-bound proteins.209,210... 

Lanthanides have been used as substitutes for calcium in calcium binding proteins since the early days in NMR [155,156]. Remarkable information was obtained on systems such as Yb(III)-substituted parvalbumin (which contains a typical calcium binding site called EF-hand [157,158]) from ID spectroscopy alone [159-164], later complemented by 2D spectroscopy [165]. More recently, pseudocontact shifts and longitudinal proton relaxation times have been used to... 

---