Protein Synthesis: Transcription and Translation

• Proteins make up living materials and consist of amino acids.
• Different proteins result from various amino acid combinations, with ribosomes manufacturing them.

Protein Functions

• Proteins help fight disease and build new body tissue
• Enzymes that speed up the rate of a reaction and are used for digestion and other chemical reactions are proteins.
• Proteins are a component of cell membranes.

Protein Synthesis

• Protein synthesis includes transcription and translation.
• DNA undergoes transcription into mRNA, which then undergoes translation into a protein.

Making Proteins: Transcription

• Transcription involves copying genetic information from DNA to RNA.
• DNA contains the genetic code, but proteins are made by ribosomes outside the nucleus, in the cytoplasm.
• DNA is too large to leave the nucleus as a double-stranded molecule, whereas RNA, is a single-stranded molecule, and can leave.
• Part of DNA unzips temporarily and serves as a template for assembling complementary nucleotides into mRNA.

mRNA

• mRNA contains a nucleotide sequence in triplet form, called codons.
• mRNA codons consist of nucleotides with nitrogenous bases like adenine, guanine, cytosine, and uracil.
• There are 64 possible codons on mRNA, but only 61 code for specific amino acids.
• For example AUG encodes methionine
• The remaining three codons consist of UGA, UAA, and UAG. These are STOP codons

mRNA in protein production

• mRNA passes through the nucleus pores with the DNA code and binds to the ribosome.

Making Proteins: Translation

• Decoding mRNA into a protein is called translation.
• Transfer RNA (tRNA) carries amino acids from the cytoplasm to the ribosome.
• Amino acids come from the food we eat, which are then rearranged into new proteins based on DNA instructions.
• A series of three adjacent bases in an mRNA molecule code for a specific amino acid, called a codon.
• Each tRNA has three nucleotides that are complementary to the codon in mRNA. and codes for a different amino acid.

tRNA

• tRNA contains nucleotide sequences in triplet form complementary to mRNA codons.
• These sequences are called anticodons.
• tRNA with complementary anticodons to mRNA codons allow tRNA to carry specific amino acids.
• As an example, the mRNA codon AUG pairs with the tRNA anticodon UAC, which carries methionine.
• tRNA anticodons exhibit a "wiggle phenomenon," where a nitrogenous base (inosine) on the 5' end of tRNA anticodon can bind to multiple nucleotides.

Protein production via mRNA and tRNA

• mRNA carries DNA instructions, and tRNA carries amino acids and they meet in the ribosomes.
• The messenger RNA is transcribed in the nucleus.
• This then enters the cytoplasm and attaches to a ribosome and then translation begins at AUG, the start codon.
• Each transfer RNA has an anticodon with bases that are complementary to a codon on the messenger RNA strand.
• The ribosome positions the start codon to attract its anticodon, which is part of the tRNA that binds methionine.
• The ribosome then binds the next codon and its anticodon.

Protein production

• Amino acids join together to form a protein.
• The ribosome joins the two amino acids, breaking the bond between methionine and its tRNA.
• The tRNA then floats away from the ribosome and allows the ribosome to bind another tRNA.
• The ribosome moves along the mRNA binding new tRNA molecules and amino acids.
• The process continues until the ribosome reaches one of the three stop codons, resulting in a complete polypeptide.

Protein Synthesis Inhibitors

• Protein synthesis inhibitors are antibiotics that bind with the ribosomal subunit of bacteria and interfere with protein synthesis.
• Protein is required for the growth and development of the organism.
• Antibiotics target the bacterial ribosome, which has components differing structurally from the mammalian cytoplasmic ribosome.
• The bacterial ribosome is smaller (70S) than the mammalian ribosome (80S).
• Bacterial ribosomes are composed of 50S and 30S subunits, while mammalian ribosomes are composed of 60S and 40S subunits.

Classes of Protein Synthesis Inhibitors

• Aminoglycosides
• Tetracyclines
• Glycylcyclines
• Macrolides/Ketolides
• Macrocyclic
• Lincosamides
• Oxazolidinones.

Aminoglycosides

• Aminoglycosides are bactericidal and function by inhibiting bacterial protein synthesis by interacting with receptor proteins on the 30S ribosomal subunit.
• Aminoglycosides diffusing through porin channels on the outer membrane and requires active uptake through the inner membrane, dependent on oxygen.
• Aminoglycosides are effective against aerobic gram-negative bacilli, especially multidrug-resistant strains like Pseudomonas aeruginosa and Klebsiella pneumoniae.
• May cause synergistic effects with a β-lactam antibiotic for serious gram-positive infections like Enterococcus faecalis.
• Resistance to aminoglycosides typically results from efflux pumps, decreased uptake, or modification and inactivation by plasmid-associated enzymes.
• Aminoglycosides do not penetrate the CSF with inflammation and exhibit inadequate absorption after oral administration.
• Inadequate absorption means they should be administered parenterally or topically.
• Adverse effects of aminoglycosides include ototoxicity and nephrotoxicity.
• High doses of aminglycosides produce a neuromuscular blockade with respiratory paralysis.
• They are structurally related to aminoglycosides and are administered intramuscularly.
• Spectinomycin is an alternative for treatment of acute gonorrhea or for gonococci resistant to penicillin, or in patients hypersensitive to penicillin.

Tetracyclines

• Tetracyclines include: Tetracycline, demeclocycline, doxycycline, minocycline
• Tetracyclines concentrate intracellularly in susceptible organisms and binds reversibly to the 30S subunit of the bacterial ribosome
• This action prevents binding of tRNA to the mRNA-ribosome complex, thereby inhibiting bacterial protein synthesis
• Coverage: Gram-negative rods: brucella, vibrio cholera, Yersinia. Gram-positive bacilli: bacillus anthracis. Spirochetes: borrelia burdorferi. Mycoplasma pneumoniae. Chlamydia species. Rickettsia
• Resistance is plasmid-mediated
• tetracyclines are adequately absorbed from the GI tract and are distributed throughout body fluids
• Therapeutic concentrations in the brain and CSF can be achieved with minocycline only
• Absorption is impaired by stomach contents and must be absorbed on an empty stomach

Tetracyclines: Pharmacokinetics

• Tetracyclines are variably but adequately absorbed from the GI tract; they can also be administered parenterally
• Tetracyclines are distributed throughout body fluids.
• Therapeutic concentrations in the brain and CSF are achievable with minocycline only.
• Absorption is impaired by stomach contents like milk and antacids.
• Many tetracyclines undergo enterohepatic recirculation.
• Doxycycline is safer to administer to individuals with impaired renal function.

Tetracycline Therapeutic uses

• Rickettsial Infections
• Cholera
• Lyme Disease
• Infections caused by chlamydia
• acne vulgaris
• Helicobacter pylori infections

Tetracycline Adverse effects

• Gastric discomfort commonly results from irritation of the gastric mucosa.
• Rarely: hepatotoxicity.
• Contraindicated for pregnant women because it harms the baby.
• Tetracycline effects calcified tissues by deposition in the bone and primary dentition in growing children resulting in discolouration.
• Phototoxicity: Exposure to the sun may result in severe sunburn and patients should wear protection.
• Vestibular dysfunction: Dizziness, vertigo, and tinnitus may occur in particular with minocycline.
• Super Infection
• Contraindications: Cannot be used inpregnant women or children less than 8 years of age

Glycylcyclines and Tigecycline

• Tigecycline is the first available member of this class.
• Tigecycline is a derivative of minocycline with the same structure as tetracyclines.
• Exhibits bacterio static action by reversibly binding to the 30S ribosomal subunit and inhibits protein translation.
• Targets complicated skin and soft tissue infections and complicated intra-abdominal infections.
• Tigecycline exhibits expanded broad-spectrum activity that includes Methicillin-resistant staphylococci (MRSA).
• Not active against Pseudomonas species.
• Tigecycline does exhibit Tetracycline resistence.
• Is well tolerated but should be monitored for the increased possibility of nausea and vomiting .
• Interacts with Warfarin and recommended monitoring the rate of anticoagulation

Macrolides & Ketolids and Chemistry

• Erythromycin is a natural product of Streptomyces erythreus
• clarithromycin and azithromycin are semi synthetic derivatives
• structurally are quite big, 14- 14 member lactone ring attached to one or more deoxy sugars
• The mechanism involves inhibiting protein synthesis by irreversibly binding to the bacterial 50S ribosomal subunit

Macrolides Therapeutic Applications

• Chlamydial, MAC, and legionnaires infections
• These agents are referred to as azithromycin and doxycycline
• Macrolides are effective against pneumonia
• Can be used for diphtheria and pertussis
• Can be used as an alternative to for patients with beta lactam issues

Macrolides

• Drug reflux through an active pump protects by methylation
• These agents are readily adsorbed through the small intestines and the Gastric
• Food can cause delays in the absorption of the drug

Select Macrolides

• Erythromycin: Esters may improve acid stability higher concentrations if given in IV
• Slightly more effective against stap and strop if given with feed
• Azithromycin slightly less effective against G+ Works better against haemophilus influenza Works great against atypical mycobacteria
• Ketolides: Effective against Macrolide due to it’s ability to bind on bacterial ribosomes and provides great modification Has structural modification making it poor substrates to the efflux bump Causes epigastric distress And ototoxicity it is important to check in interactions with cabamazepines and other drug ises that are used for metabolism

Others: Fidaxomicin

• Acts on sigma sub unit which disrupts bacteria by eliminating
• works ideally in GIT
• Narrow spectrum
• Effects Staph

Chloramohenicol

• Unique and broad spectrum used to create nitro zene

Chloramphenicol Spectrum

• Is broad and created by a ribosome and also by sterilization
• Is a rapid source and is a protodrug and the usage should be adjusted for hepatic injury’s
• Should be used as second drug choice

Toxicity/ Contraindications: Chloramphenicol

• Causes hypo sensitivity and also toxicity to the body and related anemia
• Causes vomiting along with reactions

Greys baby Syndrome

• Treatment can be triggered by toxicity
• And adults who overdose by having the reactions

Chloraphenicl Drug interactions

• Half lives of drugs and half lives of drugs depend and what can
• Cause and anti retinal issues

Clindamycin Specutr Coverage

• Can be used to treat macrocodes but works also
• treats those with and related to those issues
• Anaerobic Infections
• Treats staff infections but is best known as a
• Can be used for dental

Toxicity Contrainfications

• causes diarrhea if diarrhea is happening the agent produces a clift
• SJS and syndromes

Drug and Fate

• Cannot be used for UTI as it exists that route

Streptogramins Toxicity/ Contrainindications

• Only done by an injection and and can cause pain and problems
• Hepatic and are given to live problem agents

Linezolid

• Is G+ Spectrum
• But is very limited against anaerobes
• Its action is equal to macularides and it’s resistance is the same ribosome
• 100% Absorbant
• There is no interference with absorption
• It must be excreted by kidnry
• There’s has to be in liver.

Linezolid Therapeutic Uses

• Treats VRE
• And MRSA
• Causes Minor GI Symptoms
• But is uncommon for issues with the mylo suppression
• Can treat people for vancomyocin intercocci
• Must treat for s aurus
• GI tract can be an issue because they do not interfere with absortion
• The agents are all equal against against eugenic