Crystal structure of recombinant tyrosinase-binding protein MtaL at 1.35 Å resolution

Abstract

Mushroom tyrosinase-associated lectin-like protein (MtaL) binds to mature Agaricus bisporus tyrosinase in vivo, but the exact physiological function of MtaL is unknown. In this study, the crystal structure of recombinant MtaL is reported at 1.35 Å resolution. Comparison of its structure with that of the truncated and cleaved MtaL present in the complex with tyrosinase directly isolated from mushroom shows that the general β-trefoil fold is conserved. However, differences are detected in the loop regions, particularly in the β2-β3 loop, which is intact and not cleaved in the recombinant MtaL. Furthermore, the N-terminal tail is rotated inwards, covering the tyrosinase-binding interface. Thus, MtaL must undergo conformational changes in order to bind mature mushroom tyrosinase. Very interestingly, the β-trefoil fold has been identified to be essential for carbohydrate interaction in other lectin-like proteins. Comparison of the structures of MtaL and a ricin-B-like lectin with a bound disaccharide shows that MtaL may have a similar carbohydrate-binding site that might be involved in glycoreceptor activity.

Lectins from the Edible Mushroom Agaricus bisporus and Their Therapeutic Potentials

“…The structure of monomeric full-length Abmb [51] shows very little deviation from the protein structure in the complex with PPO3 ( Figure 6) [22]. A structural arrangement occurs at the N-terminal part, in which the flexible N-terminal rotates 90 • to expose an Abmb region that interacts with PPO3.…”

Structure and properties of AB21, a novel Agaricus bisporus protein with structural relation to bacterial pore‐forming toxins

“…Although helical bundles are very common and found in a wide variety of proteins, we believe that the reported structure of the protein dimer, formed by locking two monomers inside each other, is unique and has not been described before. The crystallographic structure of AB21 presented here adds to the small number of structures of proteins from A. bisporus that have been determined so far, namely the lectin ABL, mannitol 2‐dehydrogenase, tyrosinases abPPO3, abPPO4, and the tyrosinase‐binding protein MtaL …”

“…The crystallographic structure of AB21 presented here adds to the small number of structures of proteins from A. bisporus that have been determined so far, namely the lectin ABL, 72 mannitol 2-dehydrogenase, 73 tyrosinases abPPO3, 74 abPPO4, 75,76 and the tyrosinase-binding protein MtaL. 74,77 Enterotoxin subunits HBL-B 47 hemolytic activity, were identified in Agrocybe aegerita, Pleurotus ostreatus, and Pleurotus eryngii. [78][79][80][81] Their function in fungi remains unclear, even though they were shown to be specifically expressed during the development of fruiting bodies and their involvement in the compaction of hyphae in primordia was proposed.…”

Biological responses in Balb/c mice after long‐term parenteral administration of the light subunit of mushroom tyrosinase

“…Our preliminary study employing Swiss Webster mice as the animal model suggests that LSMT is immune tolerable after weekly intraperitoneal injection up to 28 days and 12 weeks . Further, the recently elucidated crystal structure of a recombinant full‐length LSMT (rLSMT), which is nearly identical to that of the natural LSMT isolated from the mushroom, suggests potential binding of carbohydrate capability as of CNL, a ricin‐B like lectin from Clitocybe nebularis . CNL is reported to induce maturation and activation dendritic cells, thereby stimulating the immune system but our recent characterization study with macrophage cell line suggests that such biological implication is not demonstrated by LSMT .…”