Structural characterization of activation ‘intermediate 2’ on the pathway to human gastricsin

Khan, Amir R.; Cherney, M.M.; Tarasova, Nadezhda I.; James, Michael N.G.

doi:10.1038/nsb1297-1010

Cited by 35 publications

(32 citation statements)

References 39 publications

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“…The structure of intermediate 2 reveals that the prosegment no longer obstructs the active site, as it does in the zymogen (Khan et al, 1997; Fig. 2B).…”

Section: Aspartic Proteinases and Their Zvmogensmentioning

confidence: 99%

“…The mature segments of zymogens may be subjected to large conformational changes during conversion, or they may remain unchanged. The gastric aspartic protein- ases and subtilisin undergo a major rearrangement of the first ten residues at the mature N-terminus following limited proteolysis at their pro-mature junction (James & Sielecki, 1986;Gallagher et al, 1995;Khan et al, 1997). A common feature of zymogens that are activated in low pH compartments is the critical role of salt bridges in maintaining the stability of the prosegment and its interactions with the mature segment.…”

Section: General Properties Of Activation Mechanismsmentioning

confidence: 99%

“…Finally, the structure of an intermediate form of human gastricsin has been solved by X-ray crystallography (Fig. 2B), thus providing molecular details of various stages in the activation pathway (Khan et al, 1997).…”

Section: Aspartic Proteinases and Their Zvmogensmentioning

confidence: 99%

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Molecular mechanisms for the conversion of zymogens to active proteolytic enzymes

1998

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Proteolytic enzymes are synthesized as inactive precursors, or "zymogens," to prevent unwanted protein degradation, and to enable spatial and temporal regulation of proteolytic activity. Upon sorting or appropriate compartmentalization, zymogen conversion to the active enzyme typically involves limited proteolysis and removal of an "activation segment." The sizes of activation segments range from dipeptide units to independently folding domains comprising more than 100 residues. A common form of the activation segment is an N-terminal extension of the mature enzyme, or "prosegment," that sterically blocks the active site, and thereby prevents binding of substrates. In addition to their inhibitory role, prosegments are frequently important for the folding, stability, and/or intracellular sorting of the zymogen. The mechanisms of conversion to active enzymes are diverse in nature, ranging from enzymatic or nonenzymatic cofactors that trigger activation, to a simple change in pH that results in conversion by an autocatalytic mechanism. Recent X-ray crystallographic studies of zymogens and comparisons with their active counterparts have identified the structural changes that accompany conversion. This review will focus upon the structural basis for inhibition by activation segments, as well as the molecular events that lead to the conversion of zymogens to active enzymes.

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“…The structure of intermediate 2 reveals that the prosegment no longer obstructs the active site, as it does in the zymogen (Khan et al, 1997; Fig. 2B).…”

Section: Aspartic Proteinases and Their Zvmogensmentioning

confidence: 99%

Section: General Properties Of Activation Mechanismsmentioning

confidence: 99%

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Molecular mechanisms for the conversion of zymogens to active proteolytic enzymes

1998

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“…The side chains of Asp-32 and Asp-217 are represented in red. (B) Stereo view of the molecular structure of intermediate 2 on the activation pathway of human gastricsin (17). The color scheme used is the same as in A.…”

mentioning

confidence: 99%

Structural aspects of activation pathways of aspartic protease zymogens and viral 3C protease precursors

Khan

Khazanovich-Bernstein

Bergmann

et al. 1999

Proc. Natl. Acad. Sci. U.S.A.

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The three-dimensional structures of the inactive protein precursors (zymogens) of the serine, cysteine, aspartic, and metalloprotease classes of proteolytic enzymes are known. Comparisons of these structures with those of the mature, active proteases reveal that, in general, the preformed, active conformations of the residues involved in catalysis are rendered sterically inaccessible to substrates by the residues of the zymogens' N-terminal extensions or prosegments. The prosegments interact in nonsubstrate-like fashions with the residues of the active sites in most of the cases. The gastric aspartic proteases have a well-characterized zymogen conversion pathway. Structures of human progastricsin, the inactive intermediate 2, and active human pepsin are known and have been used to define the conversion pathway. The structure of the zymogen precursor of plasmepsin II, the malarial aspartic protease, shows a new twist on the mode of inactivation used by the gastric zymogens. The prosegment of proplasmepsin disrupts the active conformation of the two catalytic aspartic acid residues by inducing a major reorientation of the two domains of the mature protease. The picornaviral 2A and 3C proteases have a chymotrypsin-like tertiary structure but with a cysteine nucleophile. These enzymes cleave themselves from the viral polyprotein in cis (intramolecular cleavage) and carry out trans cleavages of other scissile peptides important for the virus life cycle. Although the structure of the precursor viral polyprotein is unknown, it probably resembles the organization of the proenzymes of the bacterial serine proteases, subtilisin, and ␣-lytic protease. Cleavage of the prosegment is known to occur in cis for these precursor molecules.

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“…The aspartates in the catalytic site (shown in red sticks) were located within the substrate-binding cleft in the enzyme moiety and flanked by the S1 and S1' subsites. These subsites are involved in the binding of the substrate to the enzyme and play an essential role in substrate specificity (Khan, et al, 1997). The S1 subsite (~Tyr75-Gly76-X-Gly78 in pepsin numbering) is conserved and is presented as a flexible loop.…”

Section: Three-dimensional Homology Modelingmentioning

confidence: 99%

Structural and phylogenetic comparison of napsin genes: The duplication, loss of function and human-specific pseudogenization of napsin B

Nishishita

Sakai

Okamoto

et al. 2013

Gene

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Aspartic proteinases form a widely distributed protein superfamily, including cathepsin D, cathepsin E, pepsins, renin, BACE and napsin. Human napsin genes are located on human chromosome 19q13, which comprises napsin A and napsin B. Napsin B has been annotated as a pseudogene because it lacks an in-frame stop codon; its nascent chains are cotranslationally degraded. Until recently, there have been no studies concerning the molecular evolution of the napsin protein family in the human genome. In the present study, we investigated the evolution and gene organization of the napsin protein family. Napsin B orthologs are primarily distributed in primates, while napsin A orthologs are the only napsin genes in other species. The corresponding regions of napsin B in the available sequences from primate species contain an in-frame stop codon at a position equivalent to that of human napsin A. In addition, a rare single-nucleotide polymorphism (SNP) that creates a proper stop codon in human napsin B was identified using HapMap populations.Recombinant protein expression and three-dimensional comparative modeling revealed that napsin B exhibits residual activity toward synthetic aspartic protease substrates compared with napsin A, presumably through a napsin B-specific Arg287 residue. Thus, napsin B was duplicated from napsin A during the early stages of primate evolution, and the subsequent loss of napsin B function during primate evolution reflected ongoing humanspecific napsin B pseudogenization.

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Structural characterization of activation ‘intermediate 2’ on the pathway to human gastricsin

Cited by 35 publications

References 39 publications

Molecular mechanisms for the conversion of zymogens to active proteolytic enzymes

Molecular mechanisms for the conversion of zymogens to active proteolytic enzymes

Structural aspects of activation pathways of aspartic protease zymogens and viral 3C protease precursors

Structural and phylogenetic comparison of napsin genes: The duplication, loss of function and human-specific pseudogenization of napsin B

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