The structure of a metalloenzyme active site is down below(black picture). Describe, from a chemical and structural perspective, how the reactive site is designed to facilitate its catalytic reaction. The example below suggests the level of detail that is required. Make sure that you explain what the metal is doing, what the reaction is, and its biological significance.
The structure of a metalloenzyme active site is down below(black picture). Describe, from a chemical and structural perspective, how the reactive site is designed to facilitate its catalytic reaction. The example below suggests the level of detail that is required. Make sure that you explain what the metal is doing, what the reaction is, and its biological significance.
Biochemistry
9th Edition
ISBN:9781319114671
Author:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.
Publisher:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.
Chapter1: Biochemistry: An Evolving Science
Section: Chapter Questions
Problem 1P
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Question
The structure of a metalloenzyme active site is down below(black picture). Describe, from a chemical and structural perspective, how the reactive site is designed to facilitate its catalytic reaction. The example below suggests the level of detail that is required. Make sure that you explain what the metal is doing, what the reaction is, and its biological significance.
![**Figure 1: Overall Architecture of pMMO**
**(A)** Structure of *Methylocystis sp.* strain M pMMO protomer (PDB accession code 3RGR). The subunits pmoB, pmoA, and pmoC are illustrated in blue, magenta, and green, respectively. The N-terminus and C-terminus of pmoB are labeled. A yellow exogenous helix is also noted. Copper ions appear as cyan spheres, and a zinc ion is depicted as a gray sphere. Ligands are represented using a ball-and-stick model.
**(B)** Structure of *M. capsulatus* (Bath) pMMO protomer (PDB accession code 3RGB). The amino terminal domain of pmoB (spmoBd1) is shown in blue, while the carboxy terminal domain (spmoBd2) is presented in gray. Two transmembrane helices are in transparent blue. In the recombinant spmoB protein, spmoBd1 and spmoBd2 are linked by a GKLGGG sequence, with residues 172 and 265 labeled. Subunits pmoA and pmoC are depicted in transparent magenta and green, respectively. A hydrophilic patch, proposed as a triscopper active site, is marked with an asterisk. Notably, the mononuclear copper site at the spmoB domains interface is absent in *Methylocystis sp.* strain M pMMO structure.
[A color version of this figure is available online.]](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2Fd2705ec0-2034-4d28-a385-06c28bb62d2f%2Fd26f8517-c0c9-4322-8fe6-3ee126c9e958%2Frvb5xha_processed.png&w=3840&q=75)
Transcribed Image Text:**Figure 1: Overall Architecture of pMMO**
**(A)** Structure of *Methylocystis sp.* strain M pMMO protomer (PDB accession code 3RGR). The subunits pmoB, pmoA, and pmoC are illustrated in blue, magenta, and green, respectively. The N-terminus and C-terminus of pmoB are labeled. A yellow exogenous helix is also noted. Copper ions appear as cyan spheres, and a zinc ion is depicted as a gray sphere. Ligands are represented using a ball-and-stick model.
**(B)** Structure of *M. capsulatus* (Bath) pMMO protomer (PDB accession code 3RGB). The amino terminal domain of pmoB (spmoBd1) is shown in blue, while the carboxy terminal domain (spmoBd2) is presented in gray. Two transmembrane helices are in transparent blue. In the recombinant spmoB protein, spmoBd1 and spmoBd2 are linked by a GKLGGG sequence, with residues 172 and 265 labeled. Subunits pmoA and pmoC are depicted in transparent magenta and green, respectively. A hydrophilic patch, proposed as a triscopper active site, is marked with an asterisk. Notably, the mononuclear copper site at the spmoB domains interface is absent in *Methylocystis sp.* strain M pMMO structure.
[A color version of this figure is available online.]
Transcribed Image Text:**Architecture and Active Site of Particulate Methane Monooxygenase**
*Megen A Culpepper¹, Amy C Rosenzweig*
**Affiliations:**
**Abstract:**
Particulate methane monooxygenase (pMMO) is an integral membrane metalloenzyme that oxidizes methane to methanol in methanotrophic bacteria, which use methane gas as their sole carbon source. Understanding pMMO function is crucial for bioremediation applications and developing new environmentally friendly catalysts for converting methane to methanol.
Crystal structures of pMMOs from three different methanotrophs reveal a trimeric architecture, containing three copies each of the pmoB, pmoA, and pmoC subunits. There are three distinct metal centers within each protomer of the trimer: mononuclear and dinuclear copper sites in the periplasmic regions of pmoB, and a mononuclear site within the membrane that can be occupied by copper or zinc. Various models have been suggested for the pMMO active site, including dicopper, tricopper, and diiron centers.
Biochemical and spectroscopic data from pMMO and recombinant soluble fragments (spmoB proteins) suggest the active site involves copper and is located at the dicopper center in the pmoB subunit. Initial spectroscopic evidence for O(2) binding at this site has been obtained. However, questions about the active site identity and nuclearity remain and will be the focus of future studies.
**Figures:**
- **Figure 1:** Illustrates the overall architecture of pMMO, showing its trimeric structure.
- **Figure 2:** Displays the modeled metal centers within the enzyme structure, emphasizing mononuclear and dinuclear copper sites.
- **Figure 3:** Provides multiple sequence alignments of representative pMMO proteins, highlighting conserved regions.
- **Figure 4:** Shows the optical spectrum of detergent-solubilized pMMO, indicating key spectral features related to metal sites.
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