When analyzing the amino acid sequences of the globin proteins shown in this fig

Question

When analyzing the amino acid sequences of the globin proteins shown in this figure, which of the followi statements are true? A helix B helix C helix -V L[SPADKTNVKAAVNGKV GAHAGEYGAEALERMFTSFPTTKTY)F PH F Human globin Human B globin Human myoglobin VHUTPEEKSAVTALWGKVN--VDEVGGEALGRLLVVY PWTORFFESFGDL -GusDGEWOLVLNYWGK VE ADI PGHGOEVLIRLEKGHPETLEKFOKFKHL E7 F8 D helix -F-DLSHO SAaVKGHGKKVADALTNAVAHVDDM P NALSALSDLHAH K L RV SIT P D AV M GpNPKVKAHGKKVLGAFSDGLAHLONLKG1FATLSELHcpKLHY E helix F helix Human globin Human globin Human myoglobin KSEDEMKASEDLKKHGATVLTALGGIUkKKGHHEAEIKP LAOSHATKHK G helix H helix pPVNEKL-CLLVTLAARL PA E FrPAVHASLOKFLASVSTVLTSKYR Human globin Human globin Human myoglobin P EN F R L LGNVLVCVLAHH FGKEFt PPVQAAYOKVVAGVANALAHKY PVKYLEFISECTIOVLOSKHPGDFGADAOGAMNKALELFRKOMASNYKE LGFQG

Explanation / Answer

A. is correct. Glycine is a non-polar molecule and small in size. Whereas, tyrosine is polar molecule and bigger than glycine. Hence, there is high chance that the function of the myoglobin would be affected.

B. is not correct because the histidine at position E7 and F8 are conserved in all three to make the pocket for heme and bind with the heme molecule.

C. statement is correct. The F helix consist of all hydrophobic residues to make hydrophobic pocket for heme molecule. Aspartic acid is hydrophilic molecule and will most certainly destroy the functionality of protein.

D is incorrect. This is because nonconservative sustitution sites will affect the structure and function whereas conservative substitution will not necessarily disturb the protein's structure and function.

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