Structure and molecular evolution of multicopper blue proteins

Abstract

The multicopper blue protein family, which contains cupredoxin-like domains as a structural unit, is one of the most diverse groups of proteins. This protein family is divided into two functionally different types of enzymes: multicopper oxidase and nitrite reductase. Multicopper oxidase catalyzes the oxidation of the substrate and then reduces dioxygen. The structures of many multicopper oxidases are already known, and until recently they were classified into two main groups: the three- and six-domain types. Both function as monomers and have three spectroscopically different copper sites: Types I (blue), II, and III (tri-nuclear). Nitrite reductase is a closely related protein that contains Types I and II (mono-nuclear) coppers but reduces nitrite instead of dioxygen. Nitrite reductase, which consists of two domains, forms a homotrimer. Multicopper oxidase and nitrite reductase share similar structural architectures and also contain Type I copper. Therefore, it is proposed that they have a common ancestor protein. Recently, some two-domain type multicopper oxidases have been found and their crystal structures have been determined. They have a trimeric quaternary structure and contain an active site at the molecular interface such as nitrite reductase. These results support previous hypotheses and provide an insight into the molecular evolution of multicopper blue proteins.

Laccase Properties, Physiological Functions, and Evolution

“…There is a chance that they may form a separate branch of MCO evolution, as their structures are rather close to prokaryotic laccases (Figures 1 and 2). Moreover, some fungal species, for example Pleurotus ostreatus, also produce laccases that are smaller than the typical 3dMCO and consist of only two domains [11]. It is highly probable that, during evolution, bacterial 2dMCO appeared before fungal 3dMCO (Figures 1 and 2).…”

“…Three dimensional structure predictions for bacterial laccase suggest three sequentially arranged cupredoxin-like domains [5,13] and copper ligands arranged in four conserved motifs (HXHG, HXH, HXXHXH, and HCHXXXHXXXXM/L/F) typical for the MCO family [14,15]. [11] and Nakamura and Go [16]). The oval shapes represent blue-copper-binding sites.…”

New insights into the catalytic active-site structure of multicopper oxidases

“…Thus, MCOs have been proposed to function as cathodic enzymes for biofuel cells. MCOs are comprised of structural units of cupredoxin-like domains and are classified into the following three groups according to the number of domains: the two-domain type (2dMCOs), the three-domain type (3dMCOs) and the six-domain type (6dMCOs) (Komori & Higuchi, 2010). These enzymes share similar spectroscopic properties related to the copper ions in the active site.…”

Multinuclear blue copper-proteins: the evolutionary design

“…Further the МСО group is split into subgroups according to the number of domains in protein. By the present time there have been identified subgroups of two-, three-, and six-domain MCO (2d-, 3d-, and 6d-МСО) [21,22].…”

“…Generalization of the obtained data was performed in the work [22], which allowed authors of that publication to develop scheme of the MCO, into which, apart from precursors of the type As one of variants of the evolutionary process, the appearance of protein of the type [C] can be considered as the closest precursor of nitrite reductase. In the course of this process there occurred loss of the interdomain T3Cu center.…”