Question

Basal lamina structure is produced by connecting planar networks of laminins and type IV collagen.Which of the following statements about these is/are correct? A. Both laminin and type IV collagen are composed of three polypeptide chains. B. Laminin has a cruciform structure. C. Laminin and type \(\mathrm{IV}\) collagen are interconnected by a heparin sulfate proteoglycan. D. Type IV collagen contains repeating sequences of (Gly-HyPro-Y) E. All of the above.

Short answer

Answer: Options A, B, and C are correct statements about laminin and type IV collagen in the basal lamina.

Step-by-step solution

Option A

To determine if this statement is true, we need to know the composition of laminin and type IV collagen. Laminin is composed of three different polypeptide chains (α, β, and γ). Type IV collagen is also composed of three different polypeptide chains (α1, α2, and α3). Therefore, Option A is correct.

Option B

Laminin has a cruciform structure, which means it has a cross-shaped structure. This is due to the way the three polypeptide chains of laminin assemble together. So, Option B is correct.

Option C

The statement claims that laminin and type IV collagen are interconnected by a heparin sulfate proteoglycan. In the basal lamina, laminin and type IV collagen do interact with proteoglycans such as heparan sulfate proteoglycans. The proteoglycans help to stabilize the network structure. Therefore, Option C is correct.

Option D

Type IV collagen has a particular amino acid sequence, which includes repeating sequences of Gly-X-Y, where X and Y are often proline (Pro) and hydroxyproline (HyPro) residues. The statement claims that it has repeating sequences of (Gly-HyPro-Y), which would mean that the hydroxyproline residue comes before the proline residue. The actual sequence is (Gly-Pro-HyPro) or (Gly-X-Y), Therefore, Option D is not correct.

Final Answer

As we analyzed all the given options, we found that Options A, B, and C are correct statements about laminin and type IV collagen. However, Option D is not correct. So, the final answer is not E (All of the above) but rather the combination of Options A, B, and C.