Functional and structural insights into astacin metallopeptidases

Abstract

The astacins are a family of multi-domain metallopeptidases with manifold functions in metabolism. They are either secreted or membrane-anchored and are regulated by being synthesized as inactive zymogens and also by colocalizing protein inhibitors. The distinct family members consist of N-terminal signal peptides and pro-segments, zincdependent catalytic domains, further downstream extracellular domains, transmembrane anchors, and cytosolic domains. The catalytic domains of four astacins and the zymogen of one of these have been structurally characterized and shown to comprise compact ∼ 200-residue zinc-dependent moieties divided into an N-terminal and a C-terminal sub-domain by an active-site cleft. Astacins include an extended zinc-binding motif (HEXXHXXGXXH) which includes three metal ligands and groups them into the metzincin clan of metallopeptidases. In mature, unbound astacins, a conserved tyrosine acts as an additional zinc ligand, which is swung out upon substrate or inhibitor binding in a ' tyrosine switch ' motion. Other characteristic structural elements of astacin catalytic domains are three large α -helices and a fi ve-stranded β -sheet, as well as two or three disulfi de bonds. The N-terminal pro-segments are variable in length and rather unstructured. They inhibit the catalytic zinc following an ' aspartate-switch ' mechanism mediated by an aspartate embedded in a conserved motif (FXGD). Removal of the pro-segment uncovers a deep and extended active-site cleft, which in general shows preference for aspartate residues in the specifi city pocket (S 1 ′ ). Furthermore, astacins undergo major rearrangement upon activation within an ' activation domain, ' and show a slight hinge movement when binding substrates or inhibitors. In this review, we discuss the overall architecture of astacin catalytic domains and their involvement in function and zymogenic activation.

Structural basis for the sheddase function of human meprin β metalloproteinase at the plasma membrane

“…Overall, the fold of PD is reminiscent of that of the propeptide of astacin except that in the latter the N terminus is anchored to the catalytic moiety (in the absence of further domains) and helix α1 is rotated by ∼70°around a vertical axis so that it rather parallels the active-site cleft (PDB 3LQ0) (39 (39), which includes the zinc-binding aspartate. This is consistent with sequence similarity among PDs of general astacin family members being restricted to a short consensus sequence, FXGD (X stands for any residue) (32). The short PD of Mβ and other astacins contrasts with the large prosegments found in ADAMs, which actually constitute separate domains capable of inhibiting the CDs in trans (40).…”

“…Mβ is a 679-residue secreted multidomain type-I membrane MP that belongs to the astacin family within the metzincins (7,9,16,31,32). The enzyme is glycosylated and assembles into either disulfide-linked homodimers or heterodimers with the closely related meprin α-subunit (33).…”

“…This arginine is found within a segment mainly engaged in shaping the S 1 ′ pocket in astacins, the "170 loop" (32), and in Mβ it accounts for its preference for acidic residues in this subsite (Fig. S3 and ref.…”

Protein Discovery: Combined Transcriptomic and Proteomic Analyses of Venom from the Endoparasitoid Cotesia chilonis (Hymenoptera: Braconidae)

“…They act in activation of growth factors, degradation of polypeptides, serve as venom toxins of brown spiders, digest molecules and spread other toxins through host bodies [64,65,66]. A typical Tolloid structure contains an N-terminal Astacin domain and C-terminal CUB domains [65], which determine specificity.…”

“…They act in activation of growth factors, degradation of polypeptides, serve as venom toxins of brown spiders, digest molecules and spread other toxins through host bodies [64,65,66]. A typical Tolloid structure contains an N-terminal Astacin domain and C-terminal CUB domains [65], which determine specificity. Cc-Ven3 and Cc-Ven4 feature an Astacin domain (pfam01400) (Cc-Ven3: interval 45–245, E-value = 2.07e −65 ; Cc-Ven4: interval 45–238, E-value = 2.01e −70 ) (Figure 6A), and two CUB domains (pfam00431) (Cc-Ven3: interval 246–358, E-value = 3.11e −15 and interval 379–473, E-value = 1.42e −28 ; Cc-Ven4: interval 241–354, E-value = 2.25e −22 and interval 358–469, E-value = 1.13e −28 ).…”