diff --git a/lib/PDBMapSIFTSdb.py b/lib/PDBMapSIFTSdb.py
index 3626659..9ae8788 100644
--- a/lib/PDBMapSIFTSdb.py
+++ b/lib/PDBMapSIFTSdb.py
@@ -14,7 +14,7 @@
 from collections import OrderedDict
 import logging
 from Bio import pairwise2
-from Bio.SubsMat import MatrixInfo as matlist
+# unused and deprecated: from Bio.SubsMat import MatrixInfo as matlist
 from Bio.PDB import Structure
 from Bio.SeqUtils import seq1
 from lib import PDBMapSQLdb