Cysteinyl residues

Cousineau, J., and Meighen, E. A. (1977). Sequential chemical modification of a histidyl and a cysteinyl residue in bacterial luciferase. Can. J. Biochem. 55 433-438. 

Fig. 1. Iron-sulfur clusters basic building blocks. In most cases the iron is tetrahe-drally coordinated by sulfur from cysteinyl residues (and labile sulfur). Variability on coordination is allowed (see text). A, Rubredoxin type FeS4 (simplest cluster, no labile sulfur) B, plant-type ferredoxin [2Fe-2S] C, bacterial ferredoxin [3Fe-4S] D, bacterial ferredoxin and HiPIP [4Fe-4S] E, novel cluster [4Fe-2S, 20] ( hybrid cluster ).

In Desulfovibrio ferredoxins a general binding motif can be outlined, taking into account the presence of only one [3Fe-4S], one or two [4Fe-4S] cores, the substitution of one cluster by a S-S bridge, or even the replacement of the second cysteinyl residue by an aspartic acid (as in D. vulgaris Miyazaki Fdl and D. africanus Fdlll), which can, in certain conditions, coordinate a fourth iron atom to build a [4Fe-4S] 88) (Fig. 6). 

Figure 4-3. Oxidative cleavage of adjacent polypeptide chains linked by disulfide bonds (shaded) by per-formic acid (left) or reductive cleavage by 3-mercap-toethanol (right) forms two peptides that contain cysteic acid residues or cysteinyl residues, respectively.

Some proteins contain covalent disulfide (S— S) bonds that link the sulfhydryl groups of cysteinyl residues. Formation of disulfide bonds involves oxidation of the cysteinyl sulfhydryl groups and requires oxygen. Intrapolypeptide disulfide bonds further enhance the stability of the folded conformation of a peptide, while interpolypeptide disulfide bonds stabilize the quaternary structure of certain oligomeric proteins. 

Disulfide bonds between and within polypeptides stabilize tertiary and quaternary structure. However, disulfide bond formation is nonspecific. Under oxidizing conditions, a given cysteine can form a disulfide bond with the —SH of any accessible cysteinyl residue. By catalyzing disulfide exchange, the rupture of an S— bond and its reformation with a different partner cysteine, protein disulfide isomerase facilitates the formation of disulfide bonds that stabilize their native conformation. 

The cysteinyl residue in the core was oxidized with performic acid according to the method of Hirs ( ) and the oxidized core was digested with chymotrypsin for 8 hours at room temperature in a pH stat at pH 8.9. Enzyme equal to 0.5% of the substrate by weight was added at 0 and at 2 hr. The chymotryptic peptides were also separated by Dowex 50-X4 chromatography. 

Liu J, TB Gladysheva, L Lee, BP Rosen (1995) Identification of an essential cysteinyl residue in the ArsC arsenate reductase plasmid R 773. Biochemistry 34 13472-13476. 

Although also iron-sulfur proteins, the rubredoxins do not generate H2S on acidification since in this case the thiol groups are contributed by cysteinyl residues in the polypeptide chain. The function of clostridial rubredoxin is as yet unknown in Pseudomonas sp. a similar protein catalyzes the co-hydroxylation of alkanes, a reaction requiring molecular O2. 

Fig. 2. Structure of one of the two clusters of four iron —four sulfide — four cysteinyl residues of Micrococcal ferredoxin (47)...

Gorman, J.J. (1984) Fluorescent labeling of cysteinyl residues to facilitate electrophoretic isolation of proteins suitable for amino-terminal sequence analysis. Anal. Biochem. 160, 376. 

Gorman, J.J., Corino, G.L., and Mitchell, S.J. (1987) Fluorescent labeling of cysteinyl residues. Application to extensive primary structure analysis of protein on a microscale. Eur. J. Biochem. 168, 169-179. 

Griffin and co-workers (30) measured the high-field EPR spectrum of o-(methylthio)-p-cresyl as a model for the tyrosyl Y272, which is covalently cross-linked to a cysteinyl residue C228 in GO. The radical spin density is localized on... 

The state of knowledge on iron-sulfur proteins which contain non-heme iron bonded to sulfur ligands (cysteinyl residues from the protein and inorganic sulfur) has been reviewed by several authors258"264. With magnetic resonance techniques it has been possible to obtain detailed information on the nature of the active site in many of these proteins. The contributions from ENDOR have recently been summarized by Sands265 so that we shall only give an outline of the crucial points. 

Crown ethers [327] in which (L)-cysteinyl residues are connected with the polyether ring via amide bonds in the 2, 3, 11, and 12-positions exhibit... 

Amino acid variants of IL-2 have been used to investigate the relationship between retention and protein structure in gradient RPLC.22 The protein contains three cysteine residues in its primary sequence at positions 58, 105, and 125. The two located at positions 58 and 105 are linked in a disulfide bridge in the native molecule. A series of variants in which the three cysteinyl residues were replaced with serines were compared. Substitution with serine at positions 58 or 105 forces the molecule to form an unnatural disulfide between positions 125 and 58 or 105. A methionine residue located at position 104 can also be oxidized to the sulfoxide... 

The hypA proteins are small proteins of between 109 and 121 residnes. They are cysteine rich (e.g. nine cysteinyl residnes in the E. coli example) only font cysteinyl residues are conserved throughont all examples. These are arranged into two -cys-X-X-cys- motifs which suggests that these proteins may be redox proteins potentially... 

With DNA-(cytosine-C ) methyltransferases, the binding mechanism also appears to be ordered with an active-site cysteinyl residue required in the enzyme reaction path. However, in this case SAM is the second substrate. The binding mechanism appears to be random with DNA-(adenine-A ) methyl transferase. 

A class of iron-sulfur proteins lacking acid-labile sulfur, but similar in function to the ferredoxins. The iron center is coordinated by four sulfur-containing hgands, usually from cysteinyl residues. Where known, these proteins function as electron carriers. 

Thermodynamically unstable substances (structure below) that serve as enzymatic reaction intermediates and are typically formed by carboxylation carboxyl group transfer) of a sulfhydryl group on a cysteinyl residue of an enzyme. 

The copper-binding sites in copper-containing proteins are characterized by three distinct classes. In Type-1, or blue copper centers, the copper is coordinated to at least two imidazole nitrogens from two histidyl residues and one sulfur from a cysteinyl residue. Type-1 coppers have small copper hyperfine couplings and a strong visible absorption in the Cu(ll) state. Type-2 or non-blue copper... 

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