Question

The most abundant protein embedded in the outer membrane of gram negative bacteria and covalently joined to the underlying peptidoglycan is:

• A. Braun's Lipoprotein
• B. LPS Protein
• C. Porin
• D. Protein A

Hint:

Remember:
• Braun's Lipoprotein \(\rightarrow\) Links outer membrane to peptidoglycan
• Porins \(\rightarrow\) Transport channels in gram-negative bacteria
• LPS \(\rightarrow\) Endotoxin component of outer membrane \[ \text{Braun's Lipoprotein is the most abundant outer membrane protein} \]

Answer 1

The Correct Option is A

Concept: Gram-negative bacteria possess:
• An inner plasma membrane
• A thin peptidoglycan layer
• An outer membrane The outer membrane is connected to the peptidoglycan layer by a special lipoprotein called: \[ \text{Braun's Lipoprotein} \] It is the most abundant protein in the outer membrane of gram-negative bacteria and helps maintain structural stability of the cell envelope.

Step 1: Identifying the protein linked to peptidoglycan. Braun's lipoprotein:
• Is embedded in the outer membrane
• Is covalently attached to peptidoglycan
• Stabilizes the bacterial cell wall Therefore: \[ \boxed{\text{Braun's Lipoprotein}} \] is the correct answer.

Step 2: Eliminating the incorrect options.
• Option (B): LPS (Lipopolysaccharide) is a major outer membrane component but not the protein covalently attached to peptidoglycan.
• Option (C): Porins are channel proteins in the outer membrane that allow passage of small molecules, but they are not covalently linked to peptidoglycan.
• Option (D): Protein A is found in the cell wall of Staphylococcus aureus, a gram-positive bacterium. Hence, the correct answer is Braun's Lipoprotein. \[ \boxed{\text{Outer membrane} + \text{Peptidoglycan linkage} \Rightarrow \text{Braun's Lipoprotein}} \]