Dear Humans: Lamina The Living World

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Neurotransmitters

preprotachykinin A mRNA

Preprotachykinin A (PPT-A)

Sequence: Arg–Pro–Lys–Pro–Gln–Gln–Phe–Phe–Gly–Leu–Met–NH₂

TAC1 mRNA

Substance P

POMC (precursor of endorphins)

Proenkephalin (PENK)

PDYN

Enkephalins (Tyr–Gly–Gly–Phe–Met / Tyr–Gly–Gly–Phe–Leu)

μ-opioid receptor

δ-opioid receptor

NPY gene → Prepro-NPY → Neuropeptide Y (NPY)

GPCRs: Y1

Y2

Y4

Y5

Y6

OXT gene → Prepro-oxytocin → Oxytocin sequence (Cys–Tyr–Ile–Gln–Asn–Cys–Pro–Leu–Gly)

OXTR (oxytocin receptor)

MAPK pathways

AVP gene → Vasopressin sequence (Cys–Tyr–Phe–Gln–Asn–Cys–Pro–Arg–Gly)

V1 Receptor

V2 Receptor

V1b

V3 Receptor

MAPK pathways

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Rhodopsin

Lys296

11-cis-retinal

all-trans-retinal

Schiff base

Glycosylation (N-terminal)

Palmitoylation (C-terminal tail)

Phosphorylation

Opsin Protein (Apoprotein)

Seven transmembrane α-helices

Transmembrane Helices (TM1–TM7)

Extracellular N-terminus

Cytoplasmic C-Terminus

Extracellular loops

Cytoplasmic loops

GPCR scaffold

Photoreceptor membrane

Arrestin

Rhodopsin kinase

Transducin (G-protein)

Phosphodiesterase (PDE)

Functional Complexes / Processes

Rhodopsin–transducin complex

Downstream phototransduction

cGMP hydrolysis

RuBisCO

Lysine

Aspartate

Glutamate

Histidine

Phosphate Groups

Hydroxyl Groups (-OH)

C2 carbonyl group

Phosphate oxygens

Magnesium ion (Mg²⁺)

Carbamate (from Lys201)

Carbamylation of Lys201

Enolization

Ribulose-1,5-bisphosphate (RuBP)

5-carbon ketopentose (ribulose)

Positions C1 and C5 phosphates

3-phosphoglycerate (3-PGA)

β/α Barrel (TIM Barrel)

8 α-helices

8 β-strands

β-Sheet Core

β-sheets

α-Helices

N-Terminus

Cytoplasmic-facing region

C-Terminus

Small subunits (RbcS)

Small Subunit (SSU / RbcS)

Chloroplast transit peptide

Chloroplast stroma

Cofactor binding site (Mg²⁺, carbamate)

Active site residues: Lys201

Asp203

Glu204

His294

LSU–LSU interfaces

LSU–SSU interfaces

LSU–SSU interactions

Large Subunit (LSU / RbcL) / RbcL

L2 Dimer

Lx Oligomers

L8S8 holoenzyme

Quaternary structure

RuBisCO activase

Receptors - Common Anatomy

α-helices

β-sheets and loops

Disulfide bonds

Ligand-binding pocket

Phosphorylation sites

Protein interaction motifs

G-protein coupling regions

Trafficking signals

Regulatory phosphorylation sites

Anchoring/scaffolding interaction sites

7 α-helices

Transmembrane Domains

Extracellular Loops

ECL1

ECL3

Extracellular Domain

Ligand-Binding Domain (LBD)

Intracellular Loops

Cytoplasmic Domains

Cytoplasmic C-Terminus

G-proteins (GPCRs)

Kinases

Phosphatases

Scaffolding proteins

Ion flux (ionotropic receptors)

Intracellular signaling

Adrenaline Receptors

Catechol hydroxyl (-OH) group

Catechol ring

Catecholamines

Serine residues in TM5

Negatively charged aspartate residue in TM3 (Asp³·³²)

Catecholamine-Specific Binding Pocket

Extracellular Loop 2 (ECL2)

PKA phosphorylation sites

GRK phosphorylation clusters

Subtype-Specific Intracellular Loop 3 (ICL3)

β-Adrenergic Receptor Regulatory Tail

α₁ → couples to Gq

α₂ → couples to Gi

β receptors → couple to Gs

β-adrenergic receptors

Phosphorylation pattern

β-arrestin binding

Desensitization

Internalization

Resensitization

Low-affinity state (inactive)

High-affinity state (G-protein coupled)

Dopamine Receptors

Catechol ring

Aspartate residue in TM3 (Asp³·³²)

Serine residues in TM5

29–amino acid insertion in intracellular loop 3

GRK phosphorylation motifs

β-arrestin recruitment domains

Desensitization control regions

Affinity

Limbic localization

Unique intracellular loop 3 (ICL3) length

Long Intracellular Loop 3

Distinct C-terminal tail structure

Dopamine Binding Pocket (Catecholamine-Specific)

Different G-protein coupling signatures

β-arrestin signaling pathways

Excitatory pathways (Gs coupling)

Inhibitory pathways (Gi coupling)

D2S (short)

D2L (long)

D1

D2

D3

D4

D3/D4 receptors

D1 receptors

D2 receptors

D1-like family

D2-like family

DRD Subtype Variations (D1-like vs D2-like)

GABA Receptors

M2 transmembrane helices

β–α Interface

β and α subunit interaction

Coiled-coil interaction

Cl⁻ influx → hyperpolarization

GABA_B1

GABA_B2

4 transmembrane segments (M1–M4)

Central ion-conducting pore

GABA Binding Site (β–α Interface)

Benzodiazepine Allosteric Site (α–γ Interface)

Coiled-Coil C-Terminal Dimerization Domain

Gi/o Protein Coupling

Chloride Ion Channel (Cl⁻ Pore)

Venus Flytrap Extracellular Domain

Pentameric Cys-Loop

Subunits: 2α, 2β, 1γ

Obligatory Heterodimer

Diversity Layers: α (1–6)

β (1–3)

γ (1–3)

δ

ε

θ

π

ρ

Pentameric Structure

GABAA receptor (Ionotropic)

GABAB receptor (Metabotropic)

Glutamate Receptors

M3 helices

Activation gate

M3 Helix Gate

Voltage-dependent Mg²⁺ block

Cation-Selective Pore

Venus Flytrap Domain

Tetrameric Structure

Obligatory Dimer (Class C GPCR)

AMPA receptor

Kainate receptor

NMDA receptor

Glycine Receptors

Loop A

Loop B

Loop C

Aromatic Residue Cage

π–π interactions

cation–π interactions

Loop A

Loop B

Loop C (Principal Face)

Complementary Face Loops: Loop D

Loop E

Loop F

Strychnine High-Affinity Binding Site

Gephyrin-Specific Anchoring (β Subunit)

Dimerization Interface (within E-Domain)

Gephyrin

Trimerization Interface

Threefold symmetric unit

GlyR α subunits

Homopentamers

Postsynaptic scaffold lattice

Serotonin Receptors

Ionotropic (5-HT₃)

Metabotropic GPCRs (5-HT₁ → 5-HT₇)

7 transmembrane helices

intracellular loops

regulatory interactions

Ionotropic Serotonin Receptor (5-HT₃)

Pentameric structure

5-HT3A

Extracellular N-terminal domain

M1 helix

M2 helix

M3 helix

M4 helix

Extracellular N-terminus

receptor folding

ligand recognition

Transmembrane Domains: TM1

TM2

TM3

TM4

TM5

TM6

TM7

Seven alpha-helices

Extracellular Loops: ECL1

ECL2

ECL3

Intracellular Loops: ICL1

ICL2

ICL3

Histamine Receptors

Imidazole ring

Ethanolamine side chain

Asp³·³² (TM3)

Cimetidine

EL2

EL3

Intracellular loop 3 (ICL3)

H₁ → Gq (activates PLC → Ca²⁺ release)

H₂ → Gs (activates adenylyl cyclase → cAMP)

H₃ → Gi (inhibits neurotransmitter release)

H₄ → Gi (immune cell modulation)

Aspartate Receptors

α-carboxyl

β-carboxyl

Positively charged residues

Venus flytrap domain (VFT)

Ligand-induced domain closure

Ionotropic

AMPA

NMDA-like

Allosteric modulation sites

Pure excitatory neurotransmitter

Voltage-dependent gating

Co-agonists

Glutathione Receptors

Tripeptide antioxidant (γ-glutamyl-cysteinyl-glycine)

Tripeptide glutathione

Oxidized glutathione (GSSG)

GSH/GSSG ratio

Redox signaling

Detoxification

γ-glutamyl transpeptidase (GGT)

Glutathione transporters

ATP-binding cassette

MRP

ABCC